Has anyone ever played this game? It was given away by Microsoft for free during a weekend to make up for the issue they were having with Live around the winter holidays a few years back.
I really enjoy going back to play this game on occasions. It's 2D, but plays with controls similar to Shadow Complex, while not being the same type of game. Undertow is basically like a multiplayer single player game, where you battle for territories, trying to preserve your respawns and drain your enemies. There's also the occasional boss battle, but the ocean is your battle ground, so you have a large, vertical expanse to maneuver within the 2D scope.
My favorite part of the game is it's sound design, as it completely captures the underwater mechanical carnage occurring, especially for an Xbox Arcade game.
I just feel like it's a greatly under appreciated game, and really wish it had caught on better. It had cooperative play, and a versus multiplayer, but you'll never find people playing, since the community for it is dead.
Regardless, if you get the chance to play the game, I'd highly encourage it.