We visited Tulum last cruise. It was very beautiful but you can't going into the buildings anymore, they have them roped off. There is a small beach area but no fresh water showers to rinse off in.
On carnival there was an excursion for the ATV jungle excursion. You travel by ATV to a beautiful lagoon where you snorkel. My BF's family did this and loved it. Hope that helps, Carla