Inspired by films such as The Abyss, the premise of Deep Fear involves John Mayor, an ex-Navy Seal who is part of the Emergency Rescue Services battling mutants and undead humans on a naval research facility while trying to rescue a doctor from certain death.
The game's unique feature is that each room in the game is hermetically sealed, and most have a limited quantity of air. John will consume air if he stays in these areas, and will consume it a lot faster if he shoots a firearm. Should the oxygen run out in a room John will die. "Air grenades" can be found to replenish a room's air, as can first aid kits which will heal John's health and appear very similar to Resident Evil's first aid sprays.
Deep Fear's shooting takes place in third-person from varying camera angles, due to every screen in the game having a unique fixed position for its camera.