Undertow

The aquatic alien race Elect escapes from its oppressors and loads all of their people into a giant space ship known as the Ark. They settle on making earth their new home planet and launch a secret attack, melting all the polar caps covering the entire planet with water. Three different groups stand up to fight the aliens and reclaim the planet. The Iron Marines are a group of humans using what is left of technology to fight back. The second group is the Nemodian race. This group, lead by captain Nemo, has been leaving in truce with the humans for more than a hundred years at the bottom of the ocean. The final group consist of the Atlantian, a remainder of the once powerful empire of Atlantis, but trapped during the last ice age until the polar caps melted. As explained in the premise, all of the actions takes place underwater. The singleplayer portion consists of 15 missions, including cut-scenes, for one or two players in a co-op mode. As a fast-paced shooter, players command small vessels engaging different enemies. Each race has different ships, upgrades and power-ups, some of which need to be unlocked by acquiring points, through killing enemies or accomplishing team goals. Up to sixteen players can play in the versus mode, either online or through system link.