Hi Query regarding a Visa

Hi
We plan to take a cruise in Jan 2016 which will call at Sanya for a short stop after first visiting Vietnam. We hold UK passports. We will then sail on to Hong Kong. We will be in Sanya from approx 8am to 5pm. less than 24hrs.
Do we need entry permit of any sort for entry to Sanya. We do not hold a Chinese entry permit.