Games usually feature either US submarines in the Pacific Ocean, or German U-boats in the Atlantic Ocean. Most submarine simulators use World War II as the setting its submarine warfare was lengthy and intense, the historical material is extensive, and the limited capabilities of the period's submarines place a high premium on game playing skill. Submarine simulators are notable for the highly-variable pace of the game it may take hours of simulated time to get into position to attack a well-defended convoy, and sub simulators typically include an option for players to adjust the ratio of real time to simulated time up and down as desired. The usual form of the game is to go on a series of missions, each of which features a number of encounters where the goal is to sink surface ships and to survive counterattacks by destroyers. A submarine simulator is usually a computer game in which the player commands a submarine.
