A group of 12 of us went to the Nachi Cocom just last year. It was a nice out of the way beach club, not too crowded. We enjoyed the beach there very much, however there is not much else to do there if you were wanting lots of activities. You can rent a kayak if you want. We booked this excursion through islandmarketing.com it included the use of the resort pool, beach, alcoholic beverages, and also included lunch. Again, I will say it was real crowded, so if that is what you are looking for, than it is a great secluded beach resort. The adult ladies in our group found it very relaxing....however the 4 teenagers did not like the seclusion as much, they were hoping for a more populated beach with more to do for them.
Hope this helps! Our ship this year took Cozumel from it's itinerary due to the damage from the hurricanes. I was just wondering what the condition of the beaches are right now.