Hydrofool is an isometric 3D arcade adventure game released by FTL in 1987 for the Sinclair Spectrum and Amstrad CPC. It was the sequel to Sweevo's World. The game music was composed by Rob Hubbard.
Sweevo must swim through the caverns of the Deathbowl finding and pulling the plugs in the correct order. To pull a plug several puzzles must be solved using the objects that scatter the floor of the aquarium. The Deathbowl is populated by creatures which will try to stop Sweevo from carrying out his task.
Source: Wikipedia, "Hydrofool", available under the CC-BY-SA License.