Abstract: A series of three separable disk-shaped resistance members have similar openings in the central regions thereof, which, when aligned, permit two or more of the members to be grasped in the hand of the user and moved in unison through the water to exercise the arm of the user. Each resistance member has a face area which is different from the face area of the other two so the resistance members can be utilized singly or in various combinations to adjust the resistance to movement to that desired by the user. The resistance members are made of light-weight, plastic material and the larger members tend to distort when moved through the water by an adult. Reinforcement and prevention of distortion of the larger member is effected by associating one or more of the smaller members with the larger member when it is being used.