Yalong Bay is the most picture-perfect of Sanya’s beaches, though jet skis and banana boats do buzz through (there are roped-off swimming areas in the shallows). This is resort central, with all the attendant luxuries. Budget travellers will want to head to the main plaza for fast-food and coconut stands.
China’s beaches are theoretically open to everyone, but at Yalong Bay there can be a quasi-official entry fee if you’re not staying at one of the beachfront resorts. To avoid any sporadically enforced fees, walk through one of the hotels rather than entering the beach from the main square. No one will bother you.