Plates and furniture were reportedly used as weapons after a mass brawl broke out on a British cruise ship.
Six people were hurt as P&O's Britannia sailed to Southampton after a week-long trip to Norway's fjords, police said.
A man, 43, and a 41-year-old woman have been arrested on suspicion of assault.
Good Morning Britain journalist Richard Gaisford, who was on board, said an emergency tannoy summoned security staff to the ship's restaurant in the early hours of Friday.
Writing on Twitter, he said: "Witnesses told me they were so frightened they had to hide, as family groups fought," he said.
The people suspected of being behind the violence were confined to a cabin for the last day of the cruise, Mr Gaisford said.
He said the violence occurred after a black-tie evening and an afternoon of "patriotic" partying on deck, when large amounts of alcohol were consumed.
Mr Gaisford said he had been told by a witness the incident was sparked by a passenger taking offence at another holidaymaker dressed as a clown.
However, P&O denied there was someone dressed as a clown on the ship.
The buffet area was immediately sealed off as medical teams went to help the injured. Staff told me they’d never experienced anything like it and those behind the violence were confined to a cabin for the last day of the cruise, waiting for police here in Southampton.— Richard Gaisford (@richardgaisford) July 27, 2019
A P&O Cruises spokesman said: "Following an incident on board Britannia on Thursday evening we can confirm that all guests have now disembarked and the matter is now in the hands of the local police."
Hampshire Police said its officers attended the ship when it docked in Southampton and investigations are ongoing.
A police spokeswoman said: "The incident took place during the early hours of Friday, 26 July, on board P&O's Britannia while it was en route to Southampton from Bergen."
She said three men and three women were assaulted, with their injuries including significant bruising and cuts.
The man and the woman arrested, both from Chigwell, Essex, are in police custody.