This was taken off TUI Cruise page.
TESTING REQUIREMENT As a Marella Cruises safety measure, all customers aged 2 and over must complete an antigen (rapid flow) test to be taken the day before you are due to fly to Dubrovnik. The test must be taken before checking-in at your UK airport and you must produce a negative certificate at check-in. If your itinerary departs from the 1st October up to and including the 31st of October then no pre-cruise test is required for cruises departing from Dubrovnik, Croatia. Italy requires you to wear an FFP2 mask on the ship when in Italian waters and at times when ashore. Please ensure you bring FFP2 masks with you.