Strategy and simulation are the main ingredients in this sea warfare game.

As commander of an instrument-laden submarine, your mission is to seek out all enemy shipping and send it to Davy Jones's locker, while ensuring that your sub is not despatched to said locker by depth charges, hull damage or total loss of torpedoes or fuel.

The screen is split vertically into three segments, the left and right sections containing various instrument readouts while the central and larger section holds one of three main views.

The instrument displays, numerous enough to be initially bemusing, cover such essentials as speed, attitude and depth, hydrophone chart, compass, fuel and air, battery charge, and hull damage.

The central area gives either a map, sonar screen or periscope view. The map shows both your own position and that of the enemy - and even as you're looking, they're on the move. Steering your sub is fairly easy, once you've got the hang of it. Joystick up or down sends the sub rising or descending; you can crash dive or surface rapidly at the touch of a key. Moving the joystick to the left or right while keeping an eye on the attitude and compass reading controls the rudder.

Speed is handled by keys 0 to 9 though, needless to add, you move a lot slower underwater than on the surface.

The sonar screen shows any enemy ships as white blips while your position, shown as a white cross, remains static in the centre. Upping the periscope will result in a view of the surface provided you're not more than 50 feet under.

Should an enemy ship hove to while you're peering through the periscope, it will appear as a moving silhouette - then is the time to fire off a torpedo or two. More often than not, though, it'll be your ship that's doing the sinking, preceded by a violent shaking of the screen as depth charges explode around you. The sound effects really come into their own here.

Those who like their action fast and furious may not find this game their glass of grog but for those who like a slow build-up to their excitement, with both strategic and simulation elements, it should be a winner.