THe reason for Yalong Bay’s existance, if not its popularity, is the nature reserve listing of the coral reef site which is a feature on this part of Hainan island.
The Yalong Bay section is the least affected by afflictions of polution, fishing and general plundering of corals.
Tourism has become part of the economic-ecosystem which has insured the reefs continuation and the rules and regulations in the wider environment.
Yalong Bay Sanya is of particular interest because of it’s soft coral diversity.
There is some more information on the Sanya Section here.
Sanya , Yalong Bay coral reef.