Titans have imprisoned Neptina, the daughter of Neptune! They have shattered his magical trident, scattered its pieces in the air and under the sea. Without his trident, Neptune is powerless.
Proteus, faithful member of Neptune's court, longs to free the lovely mermaid. He journeys to find the missing pieces of the trident, roaming land and sea, changing from a dolphin to a seagull and back again in order to deceive Neptina's captors.
But deadly trials await Proteus. Octopuses! Tangled beds of kelp! Screaming flocks of black birds! Erupting volcanoes! Valiantly, Proteus fights on ...
The first game Fathom was designed by Rob Fulop for the Atari 2600. Dave Durran wrote the game for the Intellivision with a slightly different gameplay. Imagic later released it for the ColecoVision.