Warning about Costa Maya -- when we were there a year ago, it was not particularly well organized and the snorkel tour we did was not good. The only bad snorkeling we've ever had. If I did this port again, I would either stay on the ship and enjoy a day of scant crowds, or just hang out by this huge pool surrounded by shops, basically visible from the ship by the pier.
Check out nativeway.com or maybe it's nativewaysports.com for Sting Ray City. Great service, small boat (almost everyone out there was in a group of 50 or 60 when we went), great people. Sharon will email you back right away.