The trouble started after the Carnival Legend, which can carry more than 2,000 people, set sail from Melbourne to the French territory New Caledonia last week -- though there are disputes of exactly when and why it all began.

"This is all over a thong [flip-flop sandal] -- not a foot, a thong being stepped on," a passenger told the radio station 3AW, according to the Sydney Morning Herald. The thong's trampler apologized, the man said, but its owner threatened retaliation, and the groups began to feud.

Others, however, said a single family of about two dozen people seemed intent on provoking conflicts -- spitting in the pool, screaming in the smoking area and fighting with passengers and staff over any provocation.

"They were looking for trouble from the minute they got on the ship," Kellie Peterson told 3AW. "Anyone and everything. They even picked on a 16-year-old boy because they thought he looked at them."

After several days at sea, chaos broke out on the pool deck. It's not clear what caused the dispute, though one passenger told News.com.au that it went on for 45 minutes, some of which was recorded. Children watched from behind a row of sun chairs as dozens of adults shouted on the far end of the deck. A man got into a brief shoving match with a uniformed staff member -- a prelude of the melee to come.

In a statement to The Washington Post, Carnival confirmed "several instances [of] extremely unruly behavior" on the ship.

Some passengers described it more as a state of constant fear.

Peterson told 3AW that security warned her, her husband and their three young children not to travel the decks alone. Lisa Bolitho said she and her son simply locked themselves inside their cabin, according to the Australian Associated Press.

"We've all made several complaints, saying kids were scared," Bolitho said. "The captain said, 'What do you want me to do about it -- throw them overboard?' "

The skirmishes escalated for several days at sea, passengers said, until a massive brawl broke out in the ship's nightclub early Friday morning.