Great concept game!
I really liked, but I really can't say more about it than what the reviewer just below me already did. I'll state again, however, that the main thing going for this game is the freedom, something you didn't get at, say, Ecco the Dolphin. And the atmosphere too was killer, making it menacing to go deeper into the ocean as the music suddenly fades and then grows hostile as the surface is respectively growing distant.
5 Thumbs Up!