You are at the helm of a submarine equipped with radar, sonar, depth charge indicators, torpedoes, and fuel and temperature gauges. As commander of the submarine, you must sink the enemy ships before running out of fuel. Once your fuel level reaches 0, the game is over.

You're the commander of a World War II submarine on patrol in the Mediterranean and there are enemy convoys at all points of the compass. Your job is to sink as much enemy shipping as possible while keeping your sub intact. This is no fast-paced shoot-em-up. You're really in a sub with all of its problems and limitations-batteries that need recharging, an air supply that needs to be replenished by surfacing, and the sub's very slow speed when you're submerged.