I remember seeing some footage of Hydrophobia back when it was first announced for the Xbox 360. The water-related physics and graphics looked pretty impressive and it was officially on my radar. Then it came out to tepid overall reviews while I was in the middle of playing quite a few other games, so I just never bothered to pick it up. Since then it has been re-released with the 'Prophecy' addition to the title, and by and large the reviews were much more positive afterward, claiming that this was the definitive release to try.
The game has a Tomb Raider in water feel to it. You control a female protagonist who uses guns to deal with enemies while you solve environmental puzzles via lots of climbing and jumping. It is a tried and true formula that has been imitated quite a few times over the years, with some examples being more successful than others.