There are 3 gameplay modes; career, single patrol historical battle.
The historical mode places players into combat with a specific goal in mind, ranging from sinking a few tankers to hunting down the largest battleship ever built the Yamamoto.
The career begins with the player selecting their start date this effects the choice of Submarine available with dramatic differences in diving depth and technology, notably radar being available on the newer Submarines as well as the starting ports that are available.
After confirming choice of submarine start date and torpedo type (flawless or historically accurate with dud and premature/late detonation rates modelled). Players are placed onto the map screen with their patrol area marked with a dark square and their ship narked with a white dot,inside a white square.
On making contact with an enemy you are given the choice to ignore them or engage. If you engage the game loads the battle simulation.