I personally would cancel the tour that you booked for Grand Cayman and go to www.captainmarvins.com
and book your excursion with them. We went with them when we were there last time and had a wonderful time with them. It was the best decision we have ever made. The tour was 35$ per person and there was only 25 people on the boat with us. I booked the 830 excursion and had plenty of time to get there. We got to the site early and the stingrays were very active. When we were leaving an hour later the boats excursion was getting there and there were about 100 onboard. Way too crowded for me. For Jamaica I picked the excursion on the boat and sure was glad I did. I didnt feel that safe there. I was glad that I was in a controlled enviroment. Hope this helps.