There is some clever stuff in this atmospheric 'game'. It is more of a past time than a game. I just mess around with it every so often. It can be good to chill with, and it is great when you hook it up to a decent stereo too.
Basically, there are 10 instruments that you can play that make different sounds. These are all different types of animated marine lifeforms. You can play one type at a time only, and usually different ones of each type make similar sounds. However, the way you interact with each type is different, and this allows you to make some reasonably complex sound patterns. A couple of the types are really a bit naff, but a couple of them are really quite cool. The one where you bounce fish off the leaves of a plant is my favourite. You can vary the angle of leaves and the initial trajectory of the fish, and the rate at which the are thrown. Since the tone of the fish hitting the leaf varies with how often the leaf is struck and where on the leaf is struck and how big the leaf is, you can make some really interesting sound patterns and tweak them easily. The animations are pretty well modeled, and the whole commotion is quite artistic. This game is really cool and different.
The shame is that you cannot store your compositions or share them wirelessly.
There are 2 modes of play - you either make all of the noise, or it does it and you join in as little or as much as you like.
This is somehow a special game to me. I love the presentation, the character, the physics, the sounds, the whole concept. Checkout the youtube videos if you're not quite sure. I think it is great. It is just so different, and so well suited to the DS.