Nautilus

Nautilus is a 1982 computer game for the Atari 8-bit series created by Mike Potter and distributed by Synapse Software. The players control a submarine, the Nautilus, or a destroyer, the Colossus, attempting to either destroy or rebuild an underwater city. The game is historically notable as the first to feature a "split screen" display to allow both players to move at the same time. Source: Wikipedia, "Nautilus (video game)", available under the CC-BY-SA License.