This is one of the few tours that is open to kids 10+, so provides a nice family opportunity. You should be able to swim well, and it's best to have some snorkelling experience. You enter outside the park at guest services, so don't need park admission.
You are met in the guest services courtyard (to the right of the windows) and give clothing size info, so that when you arrive in the locker room, your wetsuit and other equipment is ready for you. There is the prerequisite training lecture, then off to put on your wetsuit. If you have never done it, it is a bit of an experience, if you have, it's funny to watch others. You then parade from the locker room to the central core through the guest aquarium area where the stairs are located to the top of the tank. You are equipped with an oxygen tank and respirator similar to scuba, (breathing is similar to using a snorkel) you have fins, mask and a flotation vest that will keep you on the surface no matter what. If you try to dive, you will look like a duck with your butt and feet in the air.
You get about 30-45 min in the tank and get to see a whole lot. Some fish and the sea turtles are very friendly and come close...but you are not to attempt to touch. You can wave at guest in the view windows. For non divers it is a very special experience.
The one down to our tour was that it was very full, and due to a scheuling mistake an additional group was added on. The tank area was really too crowded for a leisurely swim.
If you are certified, do the scuba tour, but if not, or with younger children, this is a truly wonderful experience.