Best Snorkeling

My husband wants to snorkel, but he wants to know which island would be best. He wants the clearest water possible. We haven't been to any of these islands, so which in your opinion would be the best place to snorkel with the clearest water? We're going to:

Grand Turk

Antigua

Martinique

St. Lucia

St. Kitts

St. Thomas

San Juan, Puerto Rico

We'd recommend Sapphire Beach or Coki on St Thomas, you can find excellent info on that forum!

Cookie is nice cuz it's right off the beach....