A great game, that has gone unseen.
You play as a freshly graduated cadet, and your mission is to protect your home base, by helping collect Thorium (a crystal used for energy), herd fish and kill the evil mutants, known as the Shadowkin (seriously, it's more fun than it sounds). It has a interesting plot, with many twist and turns, lets just say you are the only one capable of saving your civilisation.
It's sad that no one notice the game, as it's the best FPS underwater game I ever played (and probably the only one around).
I say, give it a go, and you will love it.