I cannot say enough good things about this tour! We booked this tour for our day in Grand Cayman while on the Caribbean Princess for our honeymoon. I booked it online after reading all of the great reviews on TripAdvisor. Mark answered all of my questions quickly via email. He met us right on the pier at Grand Cayman and told us we could shop and hang out until all of the group was there and gave us a time to meet.
They drove us on two buses to the other side of the island where we got on the boat. While the boat was not the most luxurious we saw (as some other reviewers have written), it had everything we needed: a bathroom, cold drinking water and grape juice, shade, spare cameras for sale, snorkeling equipment (included in the cost of the tour), etc.
Captain Zack drove us out to the sandbar while Mark told us what to expect and talked to us about stingrays and the safety of swimming with them.
When we got to the sandbar, Mark put the squid bucket in the water and we all got in the water. Captain Zack and Mark would catch a stingray and hold it so we could pet them, feed them, or get our pictures taken with them. They all just swam around us and some people fed them squid out of their hands.
When all of our squid was gone and everyone had their fill of the stingrays, Captain Zack took us out to a barrier reef where we snorkeled and saw a nurse shark swimming. They drove us back to the buses which took us right back to the cruise ship pier.
I would HIGHLY recommend this tour to anyone. Just book through their website. It is much cheaper and less crowded than the cruise ship tours and you can depend on them.