Arriving Shanghai by plane (from Seoul), leaving next day by cruise ship to Okinawa and onward

We are U.S. citizens. What type of visa do we need for the above layover? There are no other China stops on the cruise, except Hong Kong where we stay in port 1 night (for a total of appx. 32 hours). The next stop after we leave Shanghai is Okinawa, Japan. The final stop is Singapore.

Thank you.