Arriving by air into Shanghai to join a cruise ship

Hello, we will be arriving into Shanghai from Hong Kong most likely about 2pm and joining a cruise ship that same day, however the ship stays overnight sailing next day at 4pm. 1a)Can I get off to explore the ship the next day before it sails under the 24 or 72 hour transit visa?
Or if not
1b) would I have to stay on the ship on the next day until it sails?
Or
2) if I arrive into Shanghai after 4pm and join the ship the same day, would I be able to get off the ship the next day and explore as I am within the 24 hour transit time?
.
Many thanks James