A rapid elevation floor system for a pool at least partially filled with pool water, including a raisable floor for disposing over the bottom of the pool. The raisable floor is combined of a plurality of modular floor elements, at least some of which include a ballasting receptacle. The ballasting receptacle is adapted to receive and discharge a volume of a flotation fluid lighter than the pool water, enabling the pool water to occupy any part of the volume when unoccupied by the flotation fluid. When the raisable floor is disposed beneath the surface of the pool water, the amount of the flotation fluid contained in the raisable floor is adjusted to render the specific weight of the raisable floor as equal to, or as slightly greater than the specific weight of the pool water, such that pumping of the flotation fluid into the ballasting receptacle(s) urges a rapid elevation of the raisable floor.