I went to St. Thomas 2 years ago. I took 2 shore dives right off of Coki beach. It was well worth the $$$ low prices! Saw lots of nice stuff. Barrel sponges bigger than nail kegs. Snorkeling was great too. Locals wait on you hand and foot. We got 2 for 1 drink specials all day.
Also try to snorkel at Sapphire Beach resort. We took several a couple of day trips (including St. John). Where we were staying Sapphire beach, was as good as any place we went (go out to the point out to the left or schools of blue tangs to the right) Best snorkeling I ever been to.
We went to St Martin this past year. Boat dive on this trip, rockwork covered with every color sponge you could imagine, incredible !