We've done this island both ways!! One time we did our own thing...got off the tender boat and booked with the locals standing at the pier, the other time we booked with the cruise line. In my "humble"opinion pro's and con's for each.
When we took our chances at the pier where the tender let us off we paid our money and were to be back in an hour for the stingray sandbar tour. I think we paid 25.00 per person. We came back in one hour and the tour guide came up with this "STORY" that the tour had been postponed. The bottom line was that they had not filled up their tour boat and they were stalling. They took us and dropped us off at one of the hotel beaches (I think it was the Wyndham) on seven mile beach and came back and picked us up 2 hours later. We did finally get to see the sting rays but the boat was old and shabby and we had not planned on sitting for 2-3 hours. We wanted to see the stingrays early and then go back to the boat and clean up and then do some shopping. We still laugh about this and had a great time,but if you are a planner and don't like impulse decisions I suggest you book your tour with the cruise ship. Yes, the cruise ships make money off of the tours also. It is just a fact and we love to cruise so we don't get hung up on in anymore. The last time we went to Cayman we just booked our tour with the cruise ship. We booked the earliest available tour and we were actually the first people at the sand bar that morning. (Our tour left at 7:45 am) It was great, no waiting, we knew what to expect and by the time we left our tour all of the other boats were just pulling up. We got back in town and shopped for a couple of hours had lunch and then headed back to the cruise ship ....no rush!!
We have a great time no matter what, just figure our what style is best for you.
Sometimes its fun to do the adventurous things, others times I just don't want the worry. Have fun and know the STINGRAYS are the most AWESOME things you will ever be in contact with.. Take you underwater disposable camera's the photo's will be great!