We've been to Costa Maya twice. First time we did the Chacchoben ½ day tour which is well worth seeing. Second time we visited the port, did some shopping, had a "cool one" and layed around the ship.
The port of Costa Maya is a man made port with only a small fishing village near by. The port area itself is very well done with natives in Mayan Costume to great you as you enter the port. The shops have every variety of clothing, jewelry, souvenirs, etc. that you could want.
There is a small beach area for laying around/swimming and also a pool on the property.
There is a scarseness of tours at Costa Maya, but Princess is trying to remedy that. The bus ride to Chacchoben is one hour each way with an hour at the site.
They did have a whole day tour to Kohunlich, but it was cancelled. The bus took too long to get their and was usually late getting back to the ship.
Hope this helps.