With foam, anything can float
Almost anything that is attached to a few water woggles will float. With this concept in mind, it is effortless to think of practical games and facilities inside the pool (or a lake, or pond ─ you get it).
Grab a cutter and cut a cavity on the center of the foam, so you can fit the legs of something that would, in other cases, be supported on the ground. The woggle will keep it floating on the water.