Back to back cruise

Hi, I am from UK, going on back to back cruise in November from Shanghai. Between the 2 cruises we will stay on ship, which leaves Shanghai the same day for South Korea. Do we need to get the visa free stamp for that part or is that not needed if staying on board? Also when we arrive in Shanghai at the very end, do we apply for the 144 hour stamp on the ship before disembarking or does this need done in the cruise terminal itself? Many thanks.