This is what we did when we went last month.
Grand Cayman: I pre-booked a trip to Stingray City, and Coral Reefs through NativeWays Sports. Their rep Sharon Eubanks met us in the North Terminal which is where the tenders dock. Great lady. Since we had a later excursion she kindly offered to take us to 7 mile beach, then picked us up later. We went to the dock where we boarded a small boat, and had refreshments. Richard & Michael the 2 crewman were excellent. I HIGHLY RECOMMEND Nativeways. Cost was $30 p/p for stingray city and 2 snorkel sites, for 2.5 hours. Ship charges $49 for Stingray City alone.