We were at DC this past Sunday and after seeing what the SeaVenture actually was, we decided against it. It takes place in a very small space at the edge of the reef. It is basically people walking along the bottom of the floor at the grand reef with a breathing apparatus helmet on. They don't get to see anything different than what you would see snorkeling in the reef because it takes place in the same pool. It must not be very popular because we didn't see many people taking tours while we were there. To me, it looked annoying and time consuming because the group that we did see go down took forever to get into the water and get moving because all of the helmets that they were wearing are teathered together to the same air thing that floats above them. Just my 2 cents. If you were on the fence about doing it, I would wait until you get there to book because you can see the whole adventure from the grand reef or the platform above and decide for yourself before you spend the money.