Have been to Chankannab twice. It's beautiful! We just grabbed a cab off the pier and went to Chankannab on our own. There is an entrance fee ($12 or so per person). They have plenty of beach chairs spread around the beach and some areas where you can get out of the sun if you want to. They have a restaurant, bar, changing room, place to rent snorkel or scuba equipment, a beautiful garden, dolphin swimming, etc. I highly recommend you try snorkeling as you can do it right off the beach in shallow water and see beautiful fish! If you go in without fins be sure to bring water shoes as some of the rocks are a bit sharp. Have fun!
The beach in Chankanaab has a rocky entrance (there are rock stair entrances). That's why the snorkeling is so good. Just an FYI as some people don't think it's a beach because it doesn't have a sandy entrance. I agree with A Nicer Rose-------loved Chankanaab! We didn't do the dolphin discovery/swim. If you want to to that you must reserve that it advance.
We did the dolphin swim and loved it. Booked through dolphindiscovery.com. Best thing we did on the whole trip. Near the place where you swim with the dolphins is a beach area that has a sandy entrance. You will love it I'm sure.