Passengers on a British cruise ship descended into a bloody mass brawl — after someone in a clown costume showed up at a black-tie dinner on board, according to reports.

“’There was blood everywhere,'” tweeted UK TV journalist Richard Gaisford, who was on the P&O Cruises ship, Britannia, as it headed home to the UK from Norway. “Witnesses told me they were so frightened they had to hide, as family groups fought.”

The crazed fight broke out around 2 a.m. early Friday in a 16th-floor restaurant, according to The Telegraph.

“There was a person dressed as a clown and this upset the other passengers,” a female cruise ship entertainer told the outlet.

“Things got out of hand very quickly, people had been drinking, and there was a fight … Chairs and plates were being thrown, people were very angry … It was shocking to see and some of the staff and passengers were scared and had to hide.”

Gaisford, the chief correspondent for ITV’s Good Morning Britain, also tweeted that the brawl started because of the “clown” arriving at the formal event.

“This upset one of their party because they’d specifically booked a cruise with no fancy dress,” the journalist wrote.

“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.”

Someone else told The Telegraph that most on board were “perfectly civilized and nice individuals.”

“It was just ruined by a few drunk idiots,” the passenger said.

Police met the cruise when it docked in Southampton Saturday, with six people suffering “significant bruising and cuts,” according to authorities.

A 43-year-old man and 41-year-old woman, both from Chigwell in Essex, were arrested on suspicion of assault. They were later released from custody but remain under investigation, according to the BBC.

Most passengers would have paid almost $1,250 for the cruise on the ship described by P&O Cruises as “family friendly” and “offering a “truly memorable trip,” according to The Telegraph.

“We don’t tolerate disruptive behaviour,” a P&O spokeswoman told the paper.

“Following an incident on board Britannia we can confirm that all guests have now disembarked and the matter is now in the hands of the local police.”