Fun and different. Though there were too many C's :D The easiest notes to obtain were always C's and so I didn't get much musical variety there ^_^; Would be a nice-to-have.
But yeah haven't seen anything else like it. As another commenter mentioned, sometimes bubbles don't play sounds but I actually think it's when they're outside the range (i.e. too deep a note / too large a bubble).
Thanks for the experience ^_^ Cheers.