Nice game overall. Pretty simple and easy to understand. Wanted to point out that the click used is the left, and not the right as stated on the game page (small detail, didn't concerned me much but still).
The game itself is really nice. It's relaxing but you have to pay attention to what happens every time. As some other folks pointed out, some obstacles would make the experience more enjoyable / challenging depending on what you would want to do.
As a personal suggestion, I think that if you got different kinds of seaweed, each working differently, the experience would also be better, but maybe you have some better ideas than mine.
Either case, I'm interested on what other curious proyects you could come up with.