We were last there before hurricanes knocked it off the map a few years ago. It's just recently been put back together. So what I'm about to tell you may be OBE now; if so just forget I said anything.
The boat will dock at a pier located at a Carnival-built resort. It has controlled access in and out -- you can leave any time you like, but if you want to get back in you'll need ID, including S&S. [to be sung to the tune Hotel California]. Within the resort compound are small shops of the standard variety [jewelry, t-shirt, trinket, gewgaw], at least one but I believe two restaurant/bar deals, one of which has a swim-up bar at the central pool.
Outside the gate to this resort they were building a shopping plaza [this was 3, 4 years ago; it may be finished by now]. Needless to say, I've got no clue what's there, but I'd imagine it'd be the same type of stuff you saw inside: jewelry, t-shirts, trinkets...
A mile down the road and within sight looking south is the little fishing village of Majahual. On days when cruise ships are not there, they fish for a living; with ships in port, they convert their fishing businesses into whatever they can to draw tourists. It's right on the beach and those who 'own' part of it will rent you little straw-covered huts without walls, complete with hammock or folding chairs; you can buy beers for cheap, get massages for cheap, rent bicycles somewhere, rent kayaks, rent various other things probably including snorkling gear. There's food all over.
Their beach is inside the lagoon -- the reef is about a quarter or half mile out, and you can't miss it: it's where the waves break. Inside the lagoon the water is mostly calm and shallow.
Majahual is a great place for relaxing and doing nothing.
Desperately seeking 10th cruise for the free laundry.