I can see this activity appealing to all different groups. We chose not to do the morning in Tulum, and enjoyed the full day in the park. It was very quiet when we first arrived; the weather that day was okay. It didn't rain, but clouded over and cooled off in the afternoon. We walked up the path first on our way to the start of the river. Took maybe 15 minutes, if that. Did the bike ride later, which took 5 or less. We saw no reason to take the shuttle. The restaurants were pretty good. We left our resort late enough that we had breakfast before we left; the one breakfast place looked pretty busy. The swimming was awesome! Just keeping our heads down and looking around we got to swim around with a big ol' sting ray by ourselves for awhile. The lighthouse area is not at all as it's depicted on maps: there are no trees, chairs or hammocks out there. The walking trails on the maps are all delightful, and there are tons of iguanas and coatis around the park to see. Hanging out in a hammock in the afternoon is a great way to relax if you've had a big morning, and the dolphin tanks are viewable from the paths in several places so it's fun to watch them play. Lots of souvenir shops, but they all seem to carry the same kinds of thing. Very quiet bus ride back to the resort; seems like everyone enjoyed their day to the fullest.