I was just reading a review from someone who was there on Oct. 14th. They said, after getting there at 10:30 am, they were shuttled to the beach in a flatbed truck. When they got to the beach, they were the only people there besides the workers. The bar / restaurant opened at 11:30 so they had to wait for a drink. Snorkeling was not good. When they left at 2:00 pm, there were only 13 people there. Everyone rrom the ships went to Paradise Beach.
But, they did say it was very nice, everything was new and clean. The workers were friendly and happy to see them. The cruise lines are not doing shore excursions to Chankanaab yet so anyone who goes there is on their own. It would probably be safe to say it wouldn't be crowded. Might be quite nice to have a beach to yourselves.
There is a $2 coupon on their website so entrance fee would be $14.