I want to recommend this game because it is wonderfully crafted, the underwater world just looks fantastic and the soundtrack is also great and rather relaxing and suits the game very well. The only problem is, I found the game got very boring. I got hooked after the first 5 minutes and was thinking "this is amazing, this game is so cool", but after another half an hour of playing, I started to get bored. I'm not sure if this is because I've only played a short time and haven't unlocked a lot of things, but I just couldn't stay hooked on it.
The actual gameplay and controls are different to most games, and a little average at times when I found myself clinging to a wall when I didn't want to be there.
Another downfall of the game is the mostly black area that surrounds your screen and the game world a lot of the time. I get the point of it, you're swimming through caves and everything, but I didn't like it, it got in the way of, and ruined, the game world a little too much for me.
Overall I'd say that if this is on sale, -%50 or more, maybe pick it up and give it a go, you might enjoy it more than I did.