I also recommend Nachi Cocom. We were there on the Sensation. We didn't dock until noon. If you are on a ship that docks in the afternoon Nanci stays open longer. We went snorkeling there, my husband and I were the only 2 on the boat besides the 2 guys that took us out. When we got back the resort had cleared out and we had the entire place to ourselves. This was on Nov. 3, so it may have been where it was the slower season.
Also, I highly recommend the pictures there. Ivonne De Leon was our photographer and she is amazing. Definitely worth more than we paid for them. You get one printed out the picture and a thumb drive with the other pictures. You can look her up on facebook to see some of her work.