We used Aquamania Adventures (Lambada), leaving from Simpson Bay, to go snorkeling at Prickly Pear near Anguilla and we had a wonderful time. It's a whole day trip. Lunch, snacks and drinks are included in the price.

http://www.stmaarten-activities.com/index.php/anguilla-prickly-pear

There are other companies offering the same trip but we haven't used them.