Abstract: The spa rowing adapter is a device for installation within an existing pool or spa that transforms the pool or spa into a rowing machine. The user grips lever arms, pulling on the arms from a seated or standing position in a rowing motion. In contrast to the prior art, the spa rowing adapter uses a resistance cylinder rather than floppy resistance bands or bungee cords. The resistance cylinder provides an adjustable amount of resistance during both the extending and retracting motions. The resistance cylinder changes length in response to a force, with the resistance of the motion set by an internal mechanism. The internal mechanism is adjustable by the user through rotation of a collar.