There are three competing civilizations, one of them alien. Each has its own goals, technologies, strategies, structures and military, construction and other units that you order around. You choose which civilization you want to run. So some quick thinking and quick maneuvering are often required. The scene is a century into the future, after astronomical events and a rapid rise in sea levels make living on the surface of the Earth impossible.
People descend to the bottom of the ocean to fight and steal from each other there.
A good deal of this and other aspects of the story are provided about the two human factions and the alien beings. But none of it is particularly helpful in actual game play, except that there are 10-mission campaigns for each side that are loosely based on this history. You can also play single battles, and against others via the Internet. Creating missions Submarine Titans also has what some real-time strategy titles lack, a good mission editor that allows you to create an infinite number of single missions of your own design. This vastly extends the game's replay value and makes it either a continuing source of enjoyment in front of the home computer, or a world-class time waster.