Player two, or the computer player in a single-player game, controls the destroyer, visible in the upper pane. The ship's primary task is to ferry repair crews from the right side of the map back to the left, dropping them into an elevator that takes them to the bottom of the ocean. From there they quickly move back towards the right through a tube on the ocean floor, instantly repairing the buildings directly above them as they pass. The destroyer also drops depth charges and Barracuda missiles that attack the submarine. The missiles track the submarine and can be killed by hitting them with five torpedoes. Frogmen with limpet mines randomly appear on the sea bed and track the submarine if it passes over them. These are relatively easy to dodge in most cases, and can be killed by shooting them five times. The most dangerous enemy is normally the construction crew, who may fix one of the buildings while the "Nautilus" is inside, retrieving the core.