The snorkeling at CSS was ok when we were there in May. Unfortunately, we had lots of little mini jellyfish in the area, so our trip ended up a little short. The coral was nice and there were plenty of blue and yellow fish to look at. The problem is you're supposed to wear your life jacket the whole time, so you can't free snorkel to get better views/pics. I really enjoy water sports and did the scuba with 1-day instruction, since I am not certified, and we saw a lot more interesting sea life during the scuba dive. I am planning to snorkel only when we go back to CSS in February, but I am not expecting to be blown away by it. I have snorkeled in area of the Caribbean more well known for the snorkeling, but have not been to CN, so I don't know how it compares. It is more a relaxing float in the ocean and a boat ride, but still a lot of fun!
We've snorkeled at CSA, CN, and CSS. At CSS, they take you to a deep snorkel site (50 feet?) with a sunken boat. It is much different than the Negril snorkel spots, very cool. The snorkel boat anchors in a relatively shallow arrow, and then you swim over to the boat.
While we where there last February the snorkeling was awesome! We saw alot of clown fish, a flounder, a sting ray, & a puffer fish (blow fish). Deffinitely take your under water camera. You'll be thankful later, as I am. I just watched a few of our videos, that I shared through our facebook account. Enjoy! Best of luck to you both.