We just returned after two weeks with snorkeling every day. Creole Rock (Grand Case) has an abundance of reef fish, but you will need a kayak, Rhino tour, or another boat. We booked an enjoyable tour through Captain Alan's (Oyster Pond Marina) that went to Tintamarre, Creole Rock, and Pinel. We also went to Anguilla through Boomerang tours one day.
The best snorkeling we had this trip was at the far end of Orient Beach where Club O used to be. The reef is coming back and everyday we saw turtles, a ray or two, eels, a couple of barracudas, puffers, and tons of the usual reef fish. My husband took 3200 pics, which we are wading through. The reef is on the other side of the swim buoys, about half way down from where the yellow umbrellas start and out from the floating platform (where a barracuda likes to hang out). Just be careful of the kite surfers. We wear brightly colored swim shirts to be more visible.
Definitely glad we took our gear!