This amazing underwater toy will bring hours of underwater fun and entertainment, as well as amazement and head scratching, while the kids try to figure out how it works. Hint: This revolutionary toy glides up. The hydrofin flies underwater as if by magic, using no batteries or visible source of power. Hold it flat underwater… deeper is better... then gently let go and watch the hydrophin "swim" away, quiet and smooth as a fish. Everyone is amazed, time and time again.