OAR WITH PIVOTABLE CROSSBAR AND GRIPS CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of United States Provisional Patent Application No.63/177,106, filed April 20, 2021, titled OAR WITH PIVOTABLE CROSSBAR AND GRIPS, which is incorporated by reference herein in its entirety. FIELD OF THE INVENTION [0002] This disclosure relates generally to oars and more particularly to paddleboard oars. BACKGROUND [0003] Stand-up paddleboarding is one of the fastest growing sports in the world. Paddleboarding is a safe and accessible activity that may be enjoyed by people of all ages. It can also be a social activity, allowing family and friends to converse while exploring nature from a unique vantage point. Paddleboarding is quite affordable compared to other activities, such as skiing, requiring only a board and a paddle. [0004] Paddleboarding provides an excellent cardiovascular workout and strengthens various muscle groups, particularly the core. The present disclosure identifies, for the first time, a kinesiological and ergonomical issue with a traditional paddleboard oar or paddle. The discussion of shortcomings and needs existing in the field prior to the present invention is in no way an admission that such shortcomings and needs were recognized by those skilled in the art prior to the present disclosure. [0005] To paddle a paddleboard a user stands facing forward with feet approximately should-width apart. To perform a stroke on the right-hand side (starboard) of the paddleboard, the user grips the top of the paddle with his left hand and grips the shaft of the paddle with his right hand. To perform a stroke on the left-hand side (port) of the paddleboard, the user grips the top of the paddle with his right hand and grips the shaft of the paddle with his left hand. Paddleboarding with a traditional paddle, therefore, requires the user to switch grips on the paddle between strokes on opposite sides of the paddleboard. This disadvantage adds nothing to the exercise benefits of paddleboarding but does add significant annoyance and frustration. A user’s hands may become wet while paddleboarding, making the need to switch grips between strokes particularly likely to result in a dropped paddle. [0006] A solution to this kinesiological and ergonomical issue with traditional paddleboard oars is, therefore, needed and is hereby disclosed. BRIEF SUMMARY [0007] Various embodiments relate to an oar comprising a paddle disposed at a distal end of a paddle shaft; a crossbar disposed at the proximal end of the paddle shaft; a first grip disposed at a first lateral end of the crossbar; and a second grip disposed at a second lateral end of the crossbar. The paddle shaft may comprise a telescoping paddle shaft. [0008] The crossbar may be pivotably connected to the proximal end of the paddle shaft, for example, via a main pivot about which the crossbar may be rotatable. The crossbar may be rotatable about the main pivot by about 180 degrees. The crossbar may have a u-channel configuration adapted to envelope the paddle shaft when the crossbar is fully rotated about the main pivot. [0009] The first grip may be pivotably connected to the first lateral end of the crossbar, for example, via a first lateral pivot about which the first grip may be rotatable. The first grip may be rotatable about the first lateral pivot by about 180 degrees. The first grip may have a u-channel configuration adapted to envelope the crossbar and optionally the paddle shaft when the first grip is fully rotated about the first lateral pivot by about 180 degrees. [0010] The second grip may be pivotably connected to the second lateral end of the crossbar, for example, via a second lateral pivot about which the second grip may be rotatable. The second grip may be rotatable about the second lateral pivot by about 180 degrees. The second grip may have a u-channel configuration adapted to envelope the crossbar and optionally the paddle shaft when the second grip is fully rotated about the second lateral pivot by about 180 degrees. [0011] The crossbar may comprise a midsection rotatable about the main pivot, a first telescoping section slidably disposed on the midsection and comprising the first lateral end, and optionally a second telescoping section slidably disposed on the midsection and comprising the second lateral end. The first telescoping section may comprise a first locking mechanism adapted to restrict movement of the first telescoping section along the midsection. The second telescoping section may comprise a second locking mechanism adapted to restrict movement of the second telescoping section along the midsection. [0012] The oar may further comprise a securing strap configured to be selectively wrapped around the crossbar and the paddle shaft when the crossbar is in the first fully extended position and thereby hold the crossbar in the first fully extended position. The oar may further comprise a strap attachment feature configured to secure a first strap end of the securing strap to the crossbar and a second lateral end of the securing strap to the crossbar while the securing strap is wrapped around the crossbar and the paddle shaft. [0013] The oar may further comprise means for resisting rotation of the crossbar about the main pivot. The oar may further comprise means for releasably locking the crossbar in a first rotated position in which the first grip is rotated toward the paddle; and means for releasably locking the crossbar in a second rotated position in which the second grip may be rotated toward the paddle. The oar may further comprise means for resisting rotation of the crossbar about the main pivot toward either the first rotated position or the second rotated position. The means for resisting rotation may be adapted to provide increasing rotation resistance as the crossbar rotates about the main pivot toward either the first rotated position or the second rotated position. [0014] The crossbar may comprise at least one through-hole adjacent to the main pivot. The paddle shaft may comprise a groove around the main pivot. The groove may comprise an inclined base having a variable depth along at least a portion of the groove. The at least one through-hole and the groove may be arranged to overlap when the crossbar and the paddle shaft are pivotably connected via the main pivot. The oar may further comprise a pin extending through the at least one through-hole and into the groove. The pin may be slidably disposed against the inclined base. The oar may further comprise a spring disposed to urge the pin against the inclined base. The pin may comprise a threaded segment. The oar may further comprise a nut engaging the threaded segment. The nut may be positionable along the threaded segment to adjust tension on the spring. [0015] The crossbar may comprise a slot adjacent to the main pivot. The paddle shaft may comprise a groove around the main pivot. A spring may be disposed in the groove. The spring may have a first end engaging the paddle shaft. The spring may have a second end extending through the slot when the crossbar and the paddle shaft are pivotably connected via the main pivot. The second end of the spring may comprise a threaded segment. The oar may further comprise a nut engaging the threaded segment. The nut may be positionable along the threaded segment. The slot may have a semi-circular shape with a circumference extending at least partially around the main pivot. [0016] The crossbar may comprise at least one through-hole adjacent to the main pivot. The paddle shaft may comprise at least one bushing adjacent to the main pivot and at least one roller ball positioned within the bushing. At least a portion of the roller ball may extend through the at least one through-hole when the crossbar and the paddle shaft are pivotably connected via the main pivot. The paddle shaft may comprise a nub. The first grip may comprise a notch releasably engageable with the nub to releasably lock the crossbar to the paddle shaft. The oar may further comprise a stirrup assembly pivotably connected to the first grip. The stirrup assembly may comprise a notch releasably engageable with the nub to releasably lock the crossbar to the paddle shaft. [0017] These and other features, aspects, and advantages of various embodiments will become better understood with reference to the following description, figures, and claims. BRIEF DESCRIPTION OF THE FIGURES [0018] Many aspects of this disclosure can be better understood with reference to the following figures. [0019] Figure 1 is an example according to various embodiments, illustrating a schematic diagram of an oar with a pivotable crossbar and pivotable grips. [0020] Figure 2 is an example according to various embodiments, illustrating a schematic diagram of a pivotable grip. [0021] Figure 3 is an example according to various embodiments, illustrating a schematic diagram of a crossbar and a paddle shaft pivotably connected via a main pivot. [0022] Figure 4 is an example according to various embodiments, illustrating an exploded view of an extendable crossbar assembly. [0023] Figure 5A is an example according to various embodiments, illustrating an exploded view of an assembly for resisting rotation of the crossbar about the main pivot. [0024] Figure 5B is an example according to various embodiments illustrating a cross-sectional view through the proximal end of the paddle shaft at the second central through-hole. [0025] Figures 6A is an example, illustrating a schematic diagram of the proximal end of a paddle shaft, according to various embodiments. [0026] Figure 6B is an example according to various embodiments illustrating the proximal end of the paddle shaft engaging the crossbar or a crossbar midsection. [0027] Figure 7A is an example, illustrating a schematic diagram of the proximal end of the paddle shaft according to various embodiments. [0028] Figure 7B is an example according to various embodiments illustrating a schematic diagram showing the proximal end of the paddle shaft engaging the crossbar or a crossbar midsection. [0029] Figure 8 is an example according to various embodiments, illustrating a schematic diagram of an oar with a pivotable crossbar and pivotable grips in a fully extended configuration in which the crossbar may be releasably locked to the paddle shaft. [0030] Figure 9 is an example according to various embodiments, illustrating a schematic diagram of a grip releasably engageable with a nub on the paddle shaft. [0031] Figure 10 is an example according to various embodiments, illustrating a schematic diagram of a grip pivotably engaging a stirrup assembly that is releasably engageable with a nub on the paddle shaft. [0032] Figure 11 is an example according to various embodiments, illustrating a schematic diagram of a telescoping paddle shaft and a securing strap in a stowed position. [0033] Figure 12 is an example according to various embodiments, illustrating a schematic diagram of the telescoping paddle shaft and the securing strap in a deployed position. [0034] It should be understood that the various embodiments are not limited to the examples illustrated in the figures. DETAILED DESCRIPTION [0035] This disclosure is written to describe the invention to a person having di kill i th t h ill d t d th t thi di l i t li it d t the specific examples or embodiments described. The examples and embodiments are single instances of the invention which will make a much larger scope apparent to the person having ordinary skill in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by the person having ordinary skill in the art. It is also to be understood that the terminology used herein is for the purpose of describing examples and embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims. [0036] All the features disclosed in this specification (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to the person having ordinary skill in the art and are to be included within the spirit and purview of this application. Many variations and modifications may be made to the embodiments of the disclosure without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure. For example, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logically possible. [0037] All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (for example having the same function or result) In many instances, the term “about” may include numbers that are rounded to the nearest significant figure. [0038] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a support” includes a plurality of supports. In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings unless a contrary intention is apparent. [0039] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit (unless the context clearly dictates otherwise), between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure. [0040] As used herein, the term “disposed on” refers to a positional state indicating that one object or material is arranged in a position adjacent to the position of another object or material. The term does not require or exclude the presence of intervening objects, materials, or layers. [0041] As used herein, the terms “proximal” and “distal” refer to opposite ends of an object, specifically a paddle shaft. The distal end of a paddle shaft is the end attached to a paddle that is dipped into water during use. The proximal end is the opposite end, which is closer to the user during user. [0042] All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present disclosure is not entitled to antedate such publication by prior disclosure. Further, the dates of publication provided could be different from the actual publication dates that may need to be independently confirmed. [0043] Referring to Figure 1, various embodiments relate to an oar 100. The oar 100 may include a paddle 102 disposed at a distal end of a paddle shaft 104. The oar 100 may further include a crossbar 106 disposed at and/or pivotably connected to the proximal end of the paddle shaft 104. The oar 100 may further include a first grip 108 disposed at and/or pivotably connected to a first lateral end of the crossbar 106 and a second grip 110 disposed at and/or pivotably connected to a second lateral end of the crossbar 106. [0044] The crossbar 106 may be pivotably connected to the proximal end of the paddle shaft 104 via a main pivot 105 about which the crossbar 106 is rotatable. According to various embodiments the crossbar may be rotatable about the main pivot by about 180 degrees between a first fully extended position and a second fully extended position. In the first fully extended position, the first grip 108 may be disposed adjacent to the paddle 102 at the distal end of the paddle shaft 104, while the second grip 110 is disposed toward the proximal end of the paddle shaft. In the second fully extended position, the position of the grips may be reversed, such that the second grip 110 is disposed near the paddle 102 at the distal end of the paddle shaft, while the first grip 108 is disposed adjacent to the proximal end of the paddle shaft. [0045] Figure 2 is an example according to various embodiments, illustrating a schematic diagram of a pivotable grip 108. The first grip 108 may be pivotably connected to the first lateral end of the crossbar 106 via a first lateral pivot 107 about which the first grip 108 is rotatable. The first grip may be rotatable about the first lateral pivot 107 by about 180 degrees. According to various embodiments, the first grip 108 may have a u-channel configuration adapted to envelope the crossbar 106 and optionally the paddle shaft 104 when the first grip 108 is fully rotated about the first lateral pivot. [0046] Similarly, the second grip 110 may be pivotably connected to the second lateral end of the crossbar 106 via a second lateral pivot 109 about which the second grip 110 is rotatable. The second grip 110 may be rotatable about the second lateral pivot 109 by about 180 degrees. According to various embodiments, the second grip 110 may have a u-channel configuration adapted to envelope the crossbar 106 and optionally the paddle shaft 104 when the second grip 110 is fully rotated about the second lateral pivot 109. [0047] Still referring to Figure 2, the first grip 108, and also the second grip 110 (not shown) may have a thumb-protection extension 202 positioned to prevent a user’s thumb from being pinched by the first grip 108 or the second grip 110 (not shown) when rotated to envelop the crossbar 106. [0048] Figure 3 is an example according to various embodiments, illustrating a schematic diagram of a crossbar 106 and a paddle shaft 104 pivotably connected via a main pivot 105. According to various embodiments, the crossbar 106 may have a u-channel configuration adapted to envelope the paddle shaft 104 when the crossbar 106 is fully rotated about the main pivot 105. [0049] All components of the oar described herein may be fabricated from any suitable material. Suitable materials should have sufficient rigidity to allow the oar to be useful for paddling water and/or to allow the various components to interact or engage desirably. Suitable materials include, but are not limited to, plastics, wood, metals, composites, and combinations thereof. To enhance the strength, durability, and/or rigidity of the oar, various embodiments may include structural reinforcements, such as ribbings 302, as shown in Figure 3. [0050] Figure 4 is an example according to various embodiments, illustrating an exploded view of an extendable crossbar assembly. As shown in Figure 4, according to various embodiments the crossbar 106 may be in the form of a crossbar assembly. The crossbar assembly may include a midsection 402 rotatable about the main pivot 105, a first telescoping section 404 slidably disposed on the midsection 402 and comprising the first lateral end of the crossbar 106, and optionally a second telescoping section 406 slidably disposed on the midsection 402 and comprising the second lateral end of the crossbar 106. It is said that the second telescoping section 406 is optional, because it is possible for the midsection 402 to be integral with the second lateral end, such that only one side of the crossbar assembly has an adjustable length via a telescoping section. [0051] According to various embodiments, the first telescoping section 404 may comprise a first locking mechanism 403 adapted to restrict movement of the first telescoping section 404 along the midsection 402. The first locking mechanism 403 may, for example, include one or more portions extendable through a through-hole 408 in the first telescoping section 404 to engage one of a plurality of slots 410 on the midsection 402. Similarly, the second telescoping section 406 may comprise a second locking mechanism 405 adapted to restrict movement of the second telescoping section 406 along the midsection 402. The second locking mechanism 405 may, for example, include one or more portions extendable through a through-hole 412 in the second telescoping section 406 to engage one of a plurality of slots 414 on the midsection 402. As shown in Figure 4, the first and second locking mechanisms may be pivotably disposed on the first and second telescoping sections via one or more pivots. A variety of alternative embodiments for adjusting the length of the crossbar 106 will be readily apparent to those having ordinary skill in the art. [0052] Referring to Figures 5A, 5B, 6A, 6B, 7A, 7B, 8, 9, and 10, various embodiments may include means for releasably locking the crossbar in a first rotated position in which the first grip is rotated toward the paddle; and/or means for releasably locking the crossbar in a second rotated position in which the second grip is rotated toward the paddle. Referring to Figures 5A, 5B, 6A, 6B, 7A, and 7B, various embodiments may include means for resisting rotation of the crossbar about the main pivot, such as means for resisting rotation of the crossbar about the main pivot toward either the first rotated position or the second rotated position. According to various embodiments, the means for resisting rotation may be adapted to provide increasing rotation resistance as the crossbar rotates about the main pivot toward either the first rotated position or the second rotated position [0053] Figure 5A is an example according to various embodiments, illustrating an exploded view of an assembly for resisting rotation of the crossbar 106 or the crossbar midsection 402 about the main pivot 105. As shown in Figure 5A, the main pivot 105 involves the interoperation of a plurality of elements, including a first central through-hole 522 in the crossbar midsection 402, first washer 516, second washer 517, first bolt 518, and second bolt 519. The crossbar midsection 402 may have a hollow u-channel construction, such that the central through-hole 522, according to various embodiments, may be described as two distinct holes on either side of a central void. The hollow shape of the crossbar midsection 402 allows a head portion of the paddle shaft 104 to be placed within the crossbar midsection 402. As will be readily apparent to a person having ordinary skill in the art, the central through-hole 522 of the crossbar midsection 402 may be aligned with a second central through-hole 524 of the paddle shaft and the elements of the main pivot 105 may interoperate to allow the crossbar midsection 402 and the paddle shaft to rotate about an axis extending through through-hole 522 and through-hole 524. A person having ordinary skill in the art will also readily contemplate a variety of alternative configurations for the main pivot 105. The specific embodiment of the main pivot 105 illustrated in Figure 5A is merely one example. [0054] Still referring to Figure 5A, according to various embodiments, the crossbar 106 or the crossbar midsection 402 may include at least one through- hole 520 adjacent to the main pivot 105. As shown, the crossbar midsection 402 includes both a first through-hole 520 and a second through hole 521. [0055] The paddle shaft 104 may include a groove 508 around the second central through-hole 524, which corresponds to the position of the main pivot 105, when the oar is assembled. The groove may include an inclined base 509 having a variable depth along at least a portion of the groove 508. The inclined base 509 may include a first detent notch 503 at a first high point 502 and a second detent notch 505 at a second high point 506. The inclined base may include a first low point 504 and a second low point 507. The at least one through-hole 520 and optionally the second through-hole 521 may be arranged to be adjacent to or to be aligned with or to overlap the groove 508 when the crossbar 106 or the crossbar midsection 402 and the paddle shaft 104 are pivotably connected via the main pivot 105. [0056] According to various embodiments, the oar may further include a first pin 510, extending through the first through-hole 520 and into the groove 508, the first pin 510 may be slidably disposed against the inclined base 509. A first spring 512 may be arranged to bias the first pin 512 toward or against the inclined base 509. Optionally, according to various embodiments, the oar may further include a second pin 511, extending through the second through-hole 521 and into the groove 508, the second pin 511 may be slidably disposed against the inclined base 509. A second spring 513 may be arranged to bias the second pin 511 toward or against the inclined base 509. According to various embodiments, as the crossbar 106 or the crossbar midsection 402 is rotated about the main pivot 105, the first pin 510 and optionally the second pin 511 may slid along the inclined base 509. For example, the first pin 510 may slide along the inclined base 509 from the first low point 504 toward the first high point 502 or toward the second high point 506. As the first pin 510 slides along the base 509 toward either high point, rotation of the crossbar 106 or the crossbar midsection 402 may be hindered, slowed, or resisted due to compression of the spring 512. This slower rotation may provide a better feel to the user as the oar is used to row. According to various embodiments, the first pin 511 may releasably catch on or engage the first detent notch 503 or the second detent notch. Such engagement releasably locks the crossbar in a fully extended or rowing position, in which one grip is adjacent to the paddle and the other grip is fully extended away from the paddle. A similar action may occur with respect to the second pin 511, or any number of additional pins. [0057] According to various embodiments the first pin 510 may include a threaded segment, which may engage a first nut 514. The first nut 514 may be positionable along the threaded segment to adjust tension on the first spring 512. Similarly, the second pin 511 may have a threaded segment adapted to engage a second nut 515, which may be used to adjust tension on the second spring 513. A similar arrangement may, of course, be used on any additional pins that may be included [0058] Figure 5B is an example according to various embodiments illustrating a cross-sectional view through the proximal end of the paddle shaft 104 at the second central through-hole 524 to illustrate the inclined ramp 509. As shown, the inclined base 509 may have a variable depth. The inclined base 509 may include a first detent notch 503 at a first high point 502 and a second detent notch 505 at a second high point 506. The inclined base may include a first low point 504 and a second low point 507 (not shown). [0059] Figures 6A is an example, illustrating a schematic diagram of the proximal end of a paddle shaft, according to various embodiments. As shown in Figure 6A, the paddle shaft 105 may include a groove 603 and a spring 602 may be disposed within the groove. The spring 602 may be any suitable type of spring, including but not limited to a coiled spring as shown. The spring 602 may have a first end 605 engaging the paddle shaft and a second end 604. [0060] Figure 6B is an example according to various embodiments illustrating the proximal end of the paddle shaft 104 engaging the crossbar 106 or a crossbar midsection 402, which may include a slot 606 adjacent to the main pivot 105. The second end 604 of the spring 602 may extend through the slot 606 when the crossbar 106, 402 and the paddle shaft 104 are pivotably connected, aligned, or engaged via the main pivot 105. The second end 604 of the spring 602 may include a threaded segment, which may engage with a nut 608 that is positionable along the threaded segment. As shown, the slot 606 may have a semi-circular shape with a circumference extending at least partially around the main pivot 105. Other arrangements will be readily apparent to those having ordinary skill in the art. A purpose of the semi-circular slot 606 is to allow the user to adjust tension on the spring 602 by gripping the nut 608, rotating the second end 604 of the spring 602 along the curved slot 606, and then tightening the nut 608 to secure the second end 604 of the spring 602 to the crossbar 106, 402. The spring tension need not be adjustable according to some embodiments, so the slot 606 may also be configured as a through-hole. [0061] Figure 7A is an example, illustrating a schematic diagram of the proximal end of the paddle shaft 104 according to various embodiments. As shown, the paddle shaft 104 may include a first bushing 703 adjacent to the main pivot 105 (not shown) and a first roller ball 705 positioned within the first bushing 703. The first roller ball 705 may freely rotate within the bushing 703. Any number of bushings and roller balls may be included. For example, the paddle shaft 104 may include a second bushing 704 and a second roller ball 702 positioned within the second bushing 704. [0062] Figure 7B is an example according to various embodiments illustrating a schematic diagram of the proximal end of the paddle shaft 104 engaging the crossbar 106 or a crossbar midsection 402. The arrangement shown in Figure 7B may releasably resist rotation of the crossbar 106, 402 about the main pivot 105. The crossbar 106, 402 may include a first through-hole 707 adjacent to the main pivot 105. The first roller ball 705 may at least partially extend through the first through-hole 707 such that the paddle shaft 104 releasably engages the crossbar 106, 402 to resist rotation about the main pivot 105. Any number of through-holes may be included to correspond with the number of roller balls and bushings present in the proximal end of the paddle shaft 104. For example, the crossbar 106, 402 may include a second through-hole 706 adjacent to the main pivot 105, which may releasably engage the second roller ball 702. [0063] Figure 8 is an example according to various embodiments, illustrating a schematic diagram of an oar with a pivotable crossbar and pivotable grips in a fully extended configuration 801 in which the crossbar 106, 402 may be releasably locked to the paddle shaft 104. When the crossbar 106, 402 is releasably locked to the paddle shaft 104, rotation about the main pivot 105 is restricted, which may be useful for transporting the oar. The fully extended configuration 801 may also be a rowing configuration, when the first grip 108 is rotated by about 90 degrees. According to various embodiments, a user may be able to rotate the crossbar 106, 402 into the fully extended configuration 801, execute a stroke, then rotate the crossbar 106, 402 into a second fully extended configuration (not shown) in which the crossbar 106, 402 is rotated by about 180 degrees so that the first grip 108 is near the paddle 102 and the second grip 110 is at the top of the oar. A stroke on the opposite side of a paddleboard may then be executed by the user [0064] Figure 9 is an example according to various embodiments, illustrating a schematic diagram of a grip 110 releasably engageable with a nub 904 on the paddle shaft 104. As shown in Figure 9, according to various embodiments, the grip 110 may include a notch 902, which may releasably engage a nub 904 to releasably lock the crossbar 106 to the paddle shaft 104. This configuration is one version of the releasably locked configuration already described with reference to Figure 8. [0065] Figure 10 is an example according to various embodiments, illustrating a schematic diagram of a grip 110 pivotably engaging a stirrup assembly 1002 that is releasably engageable with a nub 904 on the paddle shaft 104. As shown, the paddle shaft 104 may include a nub 904 protruding therefrom. A stirrup assembly 1006 may be pivotably connected to the first grip 110 via a tab 1004, for example, via a pin (not shown). The stirrup assembly 1002 may include an arm 1008 defining a notch 1008, that may be releasably engageable with the nub 904 to releasably lock the crossbar to the paddle shaft. To engage and disengage the releasable lock, the user may pivot the stirrup assembly 1002 with a thumb. This configuration is another version of the releasably locked configuration already described with reference to Figure 8. [0066] Figure 11 is an example according to various embodiments, illustrating a schematic diagram of a telescoping paddle shaft 1100 and a securing strap 1102 in a stowed position. The telescoping paddle shaft 1100 includes a distal section 1104 and a proximal section 1106, and an interface 1108 therebetween. In this embodiment, the proximal section 1106 telescopes from the distal section 1104. In other embodiments, the distal section 1104 can telescope from the proximal section 1106. The distal section 1104 may, of course, be associated with a paddle (not shown). The interface 1108 selectively permits the distal section 1104 and the proximal section 1106 to move relative to each other. When a desired positional relationship between the distal section 1104 and the proximal section 1106 is reached, the interface 1108 selectively provides a clamping action that holds the distal section 1104 and the proximal section 1106 in the desired positional relationship. In this embodiment, friction holds the distal section 1104 and the proximal section 1106 in the desired positional relationship. In various other embodiments, other mechanisms known to the artisan may be used, such as mechanical interlocks etc. [0067] The paddle shaft 1100 is secured to the middle of the crossbar 1110 at the main pivot joint 1112. In this embodiment, the main pivot joint 1112 may be free of any mechanisms such as detent assemblies and the like that lock the crossbar 1110 relative to the paddle shaft 1100 in any positions between the first fully extended position and the second fully extended position. The crossbar 1110 may be, therefore, free to rotate unconstrained (other than by friction at the main pivot joint 1112) between the first fully extended position where the first grip 1114 is disposed proximate the paddle shaft 1100 and the second configuration where the second grip is disposed proximate the paddle shaft 1100. [0068] The securing strap 1102 is shown in the stowed configuration and includes a first strap end 1120 secured to the crossbar 1110 via a first end strap attachment feature 1122, and a second strap end 1124 releasably secured to the crossbar 1110 via a second end strap attachment feature 1126 (e.g., a button snap arrangement or the like). [0069] As with the other embodiments disclosed above, the first grip 1114 includes a u-channel configuration 1130 that at least partly envelopes the crossbar 1110 and/or the paddle shaft 1100 when the crossbar 1110 is in the first fully extended position. Likewise, the first grip 1114 includes the first lateral pivot joint 1132. The first grip 1114 thereby functions similar to the first grip 108 disclosed above, and the second grip (not shown in Figure 10 or Figure 11) functions similar to the second grip 110 disclosed above. [0070] Figure 12 is an example according to various embodiments, illustrating a schematic diagram of the telescoping paddle shaft 1100 and the securing strap 1102 in a deployed position. When the crossbar 1110 is in the first fully extended position shown in Figure 12, the securing strap 1102 can be placed into the deployed position shown. To transition from the stowed position to the deployed position, the second strap end 1124 is released from the second end securing strap feature 1126, the securing strap 1102 is wrapped around the crossbar 1110, and the second strap end 1124 is secured to the first end strap attachment feature 1122. In addition to securing the first strap end 110 to the crossbar 1110, the first end strap attachment feature 1122 may include another feature similar to the second end strap attachment feature 1126 that enables a connection between the second strap end 1124 to the first end strap attachment feature 1122. For example, the second strap end 1124 to the first end strap attachment feature 1122 may also connect via a button snap arrangement. [0071] Since the crossbar 1110 has the u-channel configuration, the crossbar 1110 at least partly envelopes the paddle shaft 1100 when the crossbar 1110 is in the first fully extended position. Consequently, since the securing strap 1102 is wrapped around the crossbar 1110, and the crossbar 1110 envelopes the paddle shaft 1100, the securing strap 1102 secures the paddle shaft 1100 in the crossbar 1110. Such a secured configuration may be suitable any time it is preferred that the crossbar 1110 be secured in the first fully extended position, such as extended use of the oar with the crossbar 1110 in the first fully extended position, storage of the oar, and the like. [0072] Similar to the embodiments disclosed above, when the crossbar 1110 is in the first fully extended position, the first grip 1114 abuts the crossbar 1110, at least partly envelopes the crossbar 1110, and at least partly envelopes the paddle shaft 1100. In this embodiment, the u-channel shape of the crossbar 1110 at least partly envelopes the paddle shaft 1100 therein. In this embodiment, the first grip 1114 sandwiches the first lateral end 1200 of the crossbar 1110 between the first grip 1114 and the paddle shaft 1100. As is disclosed in the various embodiments, above, when the crossbar 1110 is in the second fully extended position, the second grip may function similar to the first grip 1114. [0073] As shown in Figures 11 and 12, the first grip 1114 may have a first adjustable strap 1115 and the second grip 1117 may have a second adjustable strip 1119. The straps 1115, 1119 may be configured to allow a user to provide a comfortable fit around their hands. The straps 1115, 1119 may comprise a stretchable elastomeric material for increased comfort. Each strap 1115, 1119 may include a plurality of holes that may engage with a button to provide the above-mentioned adjustability. The straps may also include a first band and a second band to secure an end of the strap. It is to be appreciated that those having ordinary skill in the art will be readily equipped based on this disclosure to provide a variety of alternatives for adjusting the size of the grips. Finally, the first grip 1114 and the second grip 1117 may each comprise a contoured palm portion 1121 to allow a user to have a more comfortable and secure grip. The contoured palm portions 1121 may be smooth or may have a textured surface.