Abstract: Step exercise apparatus primarily intended for use in an aquatic environment such as a pool or the like. The apparatus includes a step platform maintained in elevated relation above a foundation surface by a pair of support members. The apparatus has a specific gravity greater than one so as to sink within a body of water, and slots extend through the platform to prevent entrapment of air bubbles when the platform is placed in a pool. Handles in the sides and ends of the apparatus assist the user in manipulating the apparatus while exercising in the water. Removable extension feet selectively increase the step distance between the platform and the pool bottom or other foundation surface on which the apparatus rests.