Fabulous snorkeling US Virgin Islands

[closetdisneynerd]

So I have snorkeled in Maui in a volcano crater (fabulous!) and I have snorkeled in Cozumel in the open water just beyond the cruise port (not so fabulous, coral was too far down to see anything). I'm looking at the Disney excursions and looking at some independent charters. It's hard to tell if the snorkeling in St Thomas and St. John is more towards my Hawaii experience or more towards Mexico. It will be my kids first time to snorkel, and I want them to have a great experience. Thoughts on the best locations for beautiful fish and coral?