It's believed days of fighting on board the Carnival Cruise Line ship preceded the brawl and Friday's unscheduled stop to offload the family at Eden on NSW's south coast.

A NSW Police investigation is now underway.

The brawl broke out in the early hours of Friday morning aboard the ship which was well into its 10-day cruise around the South Pacific.

Passenger Kellie says a group of troublemakers had been starting fights for a few days including in front of children playing in the pool.

"There are people walking around with cut heads and hands," she told Melbourne radio station 3AW.

David Barkho says his son phoned and begged him to call authorities after he suffered a head injury while on the ship.

His 20-year-old son said "a lot of people are bleeding, a lot of people down".

"He rang me about 1am this morning and said 'Pease dad, please dad, call the federal police'," Mr Barkho told the radio station on Friday.

Video of the scuffle, shared on social media, shows dozens of people fighting each other, security guards and other staff before the person filming the incident is confronted by staff.

Carnival general manager Jennifer Vandekreek says there were "limited and isolated events with the family in question" in the lead-up to the brawl.

"Disembarking a family from a cruise is an unprecedented incident," she told reporters in Sydney on Friday.

"It is always our last resort. We felt it was the best course of action for the safety and security of our guests and our crew."

Another video on social media shows dozens of passengers applauding, and taunting the family, as they were forced off the anchored ship and handed over to water police.

"Enjoy the rest of your cruise," one woman yells out.

The group was taken ashore and transported to Canberra where they made other travel arrangements, NSW Police said.

Carnival Cruise Line has also launched an internal investigation into the incident, company president Sture Myrmell confirmed.

He would not be drawn on the actions of staff or passengers until it was completed but said "excessive behaviour" was not tolerated by the company.

Carnival has dispatched a "care team" to support the remaining passengers who are due to finish their cruise in Melbourne on Saturday.

The incident comes after seven people were off-loaded from a P&O ship in Sydney on Sunday after a 37-year-old Russian woman allegedly struck a 21-year-old man with an empty wine bottle during a fight about 1am.

Six men were released without charge while the Russian was charged with reckless wounding and affray.

Australian Associated Press