Take command of one of seven German U-Boats during WWII and hunt down and destroy allied convoys. This is never an easy task since their escorts and aircraft are waiting to ruin your day. The level of realism, and with it the difficulty, can be set by enabling or disabling ten options, e.g. unlimited ammo, clear sight or even invulnerability.

Campaigns can be started in one of several time slots, allowing you to play for the entire war if you wish. During these campaigns you gain medals and promotions which includes the command of better submarines. You can also choose to play a single mission where you can set certain variables, e.g. number of ships or weather conditions. Specific missions aren't required because the engine "rolls up" convoys and targets, meaning every time you play the missions will change. The type and location of these missions depend on the historical time and the used submarine.

The submarine consists of several rooms where you can access the functions and instruments you'll need, e.g. the logbook in the captain's room or the fuel and battery prompt in the engine room. However, the most important functions can be brought up at any time, this includes the sea map where you set waypoints. The crew can take over certain tasks, e.g. identifying ships.