Love this game! The art is really cool, I like that you made it yourself! The crabs did move through the blocks, maybe unintended? I also love the transition at the end, it's pretty fun. It first wasn't clear what to do to me, I thought you had to avoid the crabs at first but perhaps I need to read better. It's late for me, I need to sleep ;)
The interpretation of the 'waves' theme is slightly vague to me, of course you could say 'waves -> beach' but yeah...
Anyways, great game!