The private company we used was www.islandmarketing.com
for the Stingray city and 2 stop snorkeling tour on Cayman. The crew was great, we had a nice boat, personal attention and small tour. The only tiny negative was you had to take it on yourself to get to their office about 4 - 6 blocks from the tender area on shore (an easy walk). There is no there to meet you on shore from island marketing.