Passengers on a cruise ship's maiden voyage have complained of "horrendous queues", problems with Christmas dinner reservations and a lack of internet.
P&O Cruises' Arvia left Southampton for the Canary Islands last Friday.
Welsh travel reviewers Tom Hughes-Lewis and Dominik Scott, who are on board, said the ship had "a lot of unhappy people".
P&O Cruises apologised IT problems had caused "dining issues" and delays for some guests on Christmas Day.
Passenger Adrian Harvey, from Norfolk, told the BBC the dining queue on 25 December stretched for three quarters of the ship's length on two decks.
He said he was shown to his reserved table an hour-and-a-half late only to find that it was already occupied by someone else.
In an email to the BBC, he wrote: "The queues were horrendous… there were still people waiting for main courses at 23:00.
"Queues, queues, queues at reception/internet/restaurants, even virtual queues where you make a booking… What an absolute shambles."
Mr Hughes-Lewis, from Llandysul, Ceredigion, who posts travel videos online, said he and his partner experienced minor issues with their Christmas dinner, including missing courses.
"However, we have heard from many other passengers who often come to speak to us after seeing our YouTube channel that they really did have a negative experience," he said.
"There are often queues on board, particularly for dining and reception, but we can see they are putting steps in place to address this."
P&O Cruises said it had resolved the dining issues.
In a statement, it said: "We are so sorry for those guests affected by the IT and connectivity issues on Arvia's current cruise, which caused dining issues and restaurant delays for a proportion of guests on Christmas Day.
"This service was certainly not up to our usual high standards and we wholeheartedly apologise."
The 16-deck ship, which accommodates up to 5,200 guests and 1,800 crew, is the operator's second to be powered by liquefied natural gas.
It is due to sail from Southampton to the Caribbean on 6 January before returning to Europe in the summer.
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