Some of that is even right in the Caymans itself
If you get SCUBA certified and go back (not via a cruise), the diving on the east end and north wall of Grand Cayman is spectacular. Even better, get over to Caman Brac and Little Cayman. Little Cayman's famous Bloody Bay Wall is a truly spectacular dive. IMO some of the best diving to be had in the Caribbean, especially if like wall dives.