This game is absolutely brilliant as a multiplayer experience. The servers are often quiet which is a shame, but if there are players around it's loads of fun. If you have a group of mates that play it's even better! Co-op is tons of fun and really intense too.
So the bottom line is that it's a very accomplished, multiplayer underwater FPS game. There's lots of game modes, but the standout one is the co-op, where you have to survive getting eaten for 15 minutes whilst killing as many sharks as you can. It's really tense, it's frantic and the graphics and sound are actually really good. As you're swimming around there are loads of really awesome little touches and the combination of you breathing, the limited visibility and the flippers, etc. really adds to the tension.
There are quite a few maps to play on and you can customise your diver. The really funny mode is also when one of you plays as the Great White! You then have to lurk around and kill the other divers as they fight between themselves and hunt you down!
Bottom line - this is a brilliant little indie game and I would recommend it to anyone that likes to play tense, competitive FPS games. However, the co-op mode also works brilliantly, although I do wish that you could have more than 2 players on that one.