Rich, in Grand Cayman you will tender to shore.Ship tours will get off first. It is recommended that you go to Sting Ray City to swim with the Sting Rays in the morning as they are hungry. This said, I recommend you book your swim with the rays tour for first thing in morning with the ship or Capt. Marvin. As far as the sub, we did the Atlantis sub dive which went apx. 100 Ft. below sea level (apx. 30 people). It was great to see and the best place to dive after Australia. Contact Atlantis directly to check on time schedules or maybe someone who has been on the Western Caribbean itinerary with Princess lately will have the ship tour times to help you make your plans. Whatever you do have a wonderful time. Grand Cayman is beautiful.