Is a visa required for a one day stop on a cruise ship in Shanghai?

We will be on a cruise on the Celebrity ship Millennium.
We are booked on a flight from Atlanta, Ga USA to Hong Kong. Then we will be spending 4 nights in Hong Kong, then cruising to Taipei, Okinawa and then Shanghai continuing on to Nagasaki, Kobe, Shimizu and Tokyo. We will be flying home from Tokyo.
Do we need a visa to enter Shanghai while on a ship sponsored excursion just for one day?