Gameplay
Various sea creatures swim or crawl through the ocean in each sector. They are all obstacles to avoid, lending an arcade-like quality to the gameplay.
Underwater volcanoes and sharp underwater rocks also create obstacles. In some sectors on the Expert difficulty level, strong ocean currents will force the sub in a particular direction.
The player may fire ink pellets at sea creatures, covering them with clouds of ink and rendering them temporarily harmless, in the manner of an octopus or squid. These pellets are completely ineffective against the mutated creatures in the final sector of the Voyager difficulty, and mostly ineffective against the sharks in the final sector of Expert difficulty (although they can still be used to change their patrol patterns).
Contact with obstacles or underwater life forms costs the player "life", which takes the form of oxygen. Answering a math problem incorrectly also costs oxygen. There is a friendly dolphin, named Zoom, who provides extra oxygen if you can catch it. Creatures in the final sector will remove all oxygen in one shot, sending the player back to the start.
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