We haven't done a cruise stop in Cayman, but spent a week on Grand Cayman. A highlight is Stingray City, but the package the hotel offered was crazy expensive, and we found another tour group for a fraction of the cost. The tours usually include taking a boat to Stingray city, and a couple great snorkeling spots, one right at the reef. Some of the best snorkeling ever! A google search will pull up many options for groups that do this. We used Marvins, but read about another highly rated one. We toured the Turtle Farm on our own. A person at our hotel recommended Cemetery beach, we went there for a few hours and it was the calmest water I've ever been in. We took our own snorkels and masks and there is a ton of fish to see right from shore, but no amenities. We spent one day at Rum Point which is an awesome spot, you can lounge on the provided lounge chairs, they have food and drinks, and a great beach area. There are some great restaurants right in Georgetown. Very close to the turtle farm is a cool restaurant called The Cracked Conch, we had lunch here on the patio (the main part was closed, but the patio open for lunch) and it was a great setting. Sits over the water, but surrounded by limestone and has stairs that go right down into the water for divers. They were renting diving equipment right there as well. The island is very small and I would say it's easy to get transportation on your own to plan your own day. We loved Cayman!