As usual, I have a different experience from most:

Okay food, slow, surly service, too few moorings for the number of people who want to be there & we've had maybe ONE night there that wasn't uncomfortably rolly. Every time we go there it's because I've said, "we haven't been to Cooper in a while, let's go there!" and when we leave I think, "that was just not worth it".

I haven't snorkeled there but if it's that good I might be willing to overlook the other things on a super-duper-extra calm night.