Abstract: A cyclic-action buoyant toy has no moving parts. The toy floats in water in a first, horizontal position with a port below water level to admit water into a cavity within the toy, while a siphon connected to a drain operates whenever the toy has admitted enough water to assume a second, angled position. The siphon removes water at a faster rate than the port admits water, restoring the toy to the first position, stopping the siphon, and restarting the cyclic action. One embodiment uses a single-ended siphon, while a faster-acting embodiment uses a dual-ended siphon.