From Wikipedia: SSN-21 Seawolf is a submarine simulator game designed by John W. Ratcliff and published for MS-DOS systems by Electronic Arts in 1994. The player takes command of a US Seawolf-class submarine and fights in 33 missions with targets under and above water including fast Russian attack subs, destroyers and rocket frigates. The toughest enemies are the Soviet Alfa-class and Akula-class nuclear powered attack submarine, which often guard ballistic missile submarines of Typhoon and Delta class. Missions against Kilo-class diesel submarines and other submarines are also included. Like in its predecessor, the 688 Attack Sub, in some missions, the player is requested to protect a convoy, whereas other submarines and rocket cruisers would attempt to sink the convoy. Other missions involve only sub vs. sub scenarios, some with many enemy subs but also some with allied subs, which sometimes must be protected from enemy subs.