If you're not big on beaches and water clarity I would recommend Moon Palace. Huge resort with plenty to do and great food. The downside is the ocean is greenish brown in this area due to all the sea grass in the water. Not a place to go in the ocean for a swim. However, they will bus you to their Cancun property for free and you can enjoy the clear ocean for a day. The property is older but well maintained. Check for Oldies shows. They have acts like Creedence Clearwater, Survivor, Cheap Trick etc. Moon Palace is kind of off by itself too. Cancun is about 30 minutes north and Playa about 45 minutes south. My opinion, Moon Palace is nice but you could do better.
There are so much more nicer places in Cancun and Riviera Maya than Moon Palace which has seen its day. Like Bugambilias said, the ocean is really not swim able (which I was not aware). Do some research, there are some beautiful hotels and beaches in Mexico. <img src="http://www.traveltalkonline.com/forums/images/graemlins/Umbrella.gif" alt="" />