Chankunaab park costs a little over $20 per person (more if you rent snorkel gear, which you can do as part of he entrance ticket, they had a special that included a t-shirt, a beer, entrance, and snorkeling gear, which is what we got, I think we paid something like $28 per person).
The taxi takes about 10 minutes to get there. I can't remember the cost, but it wasn't extortionate.
The sand is blonde. There is a pool with swim up bar. They have a dolphin area and a sea lion show. You can watch the sea lion show and do a tour of the dolphin area for free with admission. There are chairs with shade and chairs in the sun and an area to shower the salt off after swimming or snorkeling. There are a couple of bars and there is no smoking in the park.
I used to go semi-regularly to Cozumel to dive, so March was my first actual visit to the park because I was on a cruise with my sister who does not dive. It was quite nice.