Fantastic Voyage is a side-scrolling shooter based on the 1966 movie of the same name. The scientist Jan Benes is near death because of a clot of blood in his brain. A submarine, controlled by the player, is shrunk and needs to reach the brain through three levels. The enemies, which lower the energy bar when touched, are the human defense systems like antibody cells.
Besides shooting enemies, there are also various passages in which the player needs to guide the submarine through narrow corridors without touching the environment. On the way the player needs to collect nine circuit boards required to destroy the blood cot; those may be hidden in dead ends or alternate ways. This means the player can move back and forth to try other routes at forks. It is important to pick up oxygen and fuel canisters in order to keep the submarine functional. Shield energy can be refilled by killing three enemies without missing a shot.