In the game, in addition to your submarine, there are many units of different types, each with its own characteristics and depicted on the map with different symbols and images.
The units can be either military (warships, airplanes, torpedoes, depth charges) or commercial (cargo ships or passenger ships).
They can be part of 3 groups:
At the beginning of each new game (in addition to your submarine and Torpedoes Transport) 100 random units are created on the map: 20 allied units, 20 neutral units and 60 enemy units.
When any unit is sunk or goes out of the map, a new random unit is created and enters in the game from the edge of the map, so you always have 20 allied units, 20 neutral units and 60 enemy units.
To make the game more exciting, every enemy unit is created with a route that points to your submarine, so if you remain always stop you will always have dozens and dozens of incoming enemy ships !!
Allied units :
Allied units are shown on the map with a blue symbol (except the Torpedoes Transport, in purple), they are useful because in some cases can help your submarine in the battles and especially because they can reveal via radio the position of other enemy units in their vicinity.
The submarine, Torpedoes Transport, warships, commercial ships, airplanes and your torpedoes are part of your allied units.
The allied warships look for enemy warships, report their position, go to meet them and then attack them, instead they ignore the enemy commercial ships and other neutral units.
Allied commercial ships simply follow their route.
Allied airplanes also follow their route but report with their radio the position of other units they meet.
If you sink an allied ship, the double of its tonnage is subtracted from your score.
Be careful with allied warships, if you are not identified in time they will think that you are an enemy submarine and try to attack you !!
Enemy units :
Enemy units are shown on the map with a red symbol and your task is to search for them and sink them in order to increase your score.
Warships, commercial ships, airplanes and depth charges are part of enemy units.
The enemy warships look for your submarine, Torpedoes Transport and allied warships, then go to meet them and try to destroy them.
Enemy commercial ships follow their route, they try to avoid your submarine but some of them have cannons and can attack you.
Enemy airplanes also look for your submarine, but they can attack you with their guns and depth charges.
If you sink an enemy ship, its tonnage is added to your score.
Neutral units :
Neutral units are composed only by commercial ships, they simply follow their route and should not be attacked or destroyed.
Are depicted on the map with a black symbol.
If you sink a neutral ship, its tonnage is subtracted from your score.
Allied and enemy merchant ships are often grouped in small or big convoys, and very often these convoys are protected by warships; be careful when you decide to attack a protected convoy, it can be really an hard task !
Biggest convoys can have up to 20 merchant ships protected by 18 warships !!
Unit types :
Commercial ships ->
Depth charges ->