The invention involves a paddleboard kit for converting any water sports board such as a surfboard into a paddleboard. An oar support assembly, typically secures oars with pivotal paddles to the board; facilitating rowing exercises that may be practiced while kneeling or standing. During use, the pivotable paddles pivot in such a way that the blade portion holds a steady position in relation to a shaft portion on the power stroke, while being free to fold in the opposite sense on the idle stroke when each stroke is executed as a substantially axial thrust of the shaft. The oar support assembly secures the pair of oars and is itself secured to the board by way of board couplers adjustably coupled to a portion of a strap that tightens to snuggly wrap around the board.