Abstract: The Reverse Thrust Flipper is a swimming flipper similar to a regular swimming (scuba diving, exercise, recreational) flipper that has the function of generating thrust in the opposite direction to the swimmers direction. The purpose of this flipper is to allow the swimmer to exercise without the need of a large body of water. The flipper's reverse thrust reduces de forward movement while still requiring the swimmer to exert the same amount of work. Its oscillating fin makes it possible to produce the reverse thrust in both the upward and downward leg strokes, thus maximizing the work out and enabling a simulated forward swimming experience.