GATO is a real-time 3D submarine simulation game, where the player is a commander of a United States submarine in the Pacific Ocean during World War II against Japanese warships. Gameplay consists of missions where the primary directive is to navigate the submarine to track and intercept (multiple) enemy warships (patrol boats, destroyers, etc.) on the randomly created map (which consists of randomly placed islands) and close in for the kill with torpedoes. Combat itself consists of a direct visual of enemy ships (via periscope) and firing torpedoes at the correct angle to ultimately sink the ship. Be warned that although the player has the element of surprise of a submerged vessel, enemy ships will return fire. When all hell breaks loose, a disclosed submarine is a sitting duck to Japanese guns. Be prepared to direct the damage control team to fix up the damaged submarine when under fire. The mission ends when the player has successfully eliminated all targets on the map.