Cruising from Shanghai - do I need a visa?

We arrive from the UK at Pudong Int airport 48 hours before the 5 day cruise from Shanghai to Japan (we don’t visit anywhere else in China) We then cruise back to Shanghai and fly back to the UK 24 hours after we disembark.

I’m confused as the whether we will be covered by the 144 hour exemption policy? Can we use it at the airport when we arrive on day 1, then again at the cruise port when we arrive back in Shanghai after the cruise?

Any help or advice would be much appreciated :)