I was on the Zenith on the Jan6th cruise. I dont remember the name of the dock, but it is really not near anything. There is a small town accessible by a short taxi ride, called Majahual, I think. Also about an hours drive away are some interesting Mayan ruins. There are some nice shops on the dock at Costa maya, but the shopkeepers, were awfully agressive, and you had to bargain for everything here. Unless you are a good bargainer, wait till you get to Cozumel, because you will get everything there, probably at a lower cost. I heard there was a nice beach nearby. there is a tour called the Jungle beach break, that has continuous shuttle service to and from the peir. the area beyond the peir is very unpopulated and quite forested. In this case, I think it is best to keep with a tour arranged from the ship.
Enjoy your cruise.