P&O Cruises has said that anyone wanting to take its cruises around the British Isles this summer will need to be vaccinated first.
Travellers will have to prove that they have had two coronavirus jabs to take the trips which depart from June.
Saga Cruises and Virgin Voyages in the US have made similar moves recently.
It comes amid renewed fears about the damaged travel industry, with airports warning that summer 2020 passenger numbers were their lowest since 1975.
P&O Cruises, which is part of the Carnival group, will run trips on two ships this summer. The Britannia will cruise from Southampton along the south coast of England for three or four days, and the Iona will travel up to Scotland from Southampton for seven-day trips.
Carnival said that passengers wishing to board would have to have had both vaccination jabs at least a week before departure.
Guests will also have to have travel insurance that “must include medical and repatriation cover” and medical expenses related to Covid-19.
Guests and crew will be expected to respect social distancing rules and wear masks when appropriate.
And should anyone test positive on board, they will be isolated and quarantined.
Paul Ludlow, the president of P&O Cruises, said Carnival expected a government-approved way to prove people had been vaccinated by the summer.
“This is moving at pace,” he said. “We anticipate by the 27 June, which is our first sailing, there will be a government checkmated scheme to prove your vaccination, but at the very least, then of course, a letter from your GP would suffice.
He said that P&O Cruises was “in close conversation with government every day” about travellers being able to prove their Vaccination status.