Yay, I have the game! It looks beautiful, much better than the first (which already looked good). Controls are unchanged. except you can use a CC, but I think the Wiimote is better suited for this game.
It has much more story this time around though. The beginning is extremely slow. Also, I haven't found a way to choose the exact spot where I want to dive, which annoys me a bit (but just a bit), but you can travel around the Earth diving in all the oceans, seas and many rivers.
You cannot cuddle fishes anymore. No big loss there.
All in all, the game is improved graphically, has a heavier focus on story, is much more expansive and feature-packed. And it's still only €30, so if you're interested in this type of game, pick it up!