Octopus features three old-fashioned scuba divers, attempting to evade the tentactles of the titular Octopus, in order to retrieve the sunken treasure from a shipwreck. The tentacles will move at random, so patience and good reflexes are required to get through. The player earns one point for each piece of treasure they grab, and an extra three points for returning their haul to the boat. The Octopus will move faster as the game progresses. In GAME B, the Octopus moves even faster by default.