Do we need a Visa if we are South African citizens visiting Sanya,China for 9 hours by cruise ship?

We are a family of 6 traveling in December doing a cruise from Singapore to Hong Kong. The ship docks in Sanya, China for 9 hours en route to Hong Kong. We will want to get off the ship and go into the City. Will we need to get an entry permit to do so?

If we can get a Stay permit at the Frontier Inspection Office in the Port, what would that cost per person?

Please advise.
Many thanks.
Shannon