One woman was taken to hospital while another ended up in the water and six people were charged after two separate fights at Sydney's Darling Harbour led to riot police being called.

New South Wales Police were called to the tourist precinct last night to break up a brawl about 10:45pm.

While no charges were laid as part of that incident, police were quickly diverted to a another fight when a party boat, which had dozens of people on board, docked nearby.

Police said the vessel had returned to King Street Wharf to remove a "severely intoxicated person".

As the vessel again left the dock, a number of people on board called out to passers-by to alert them to a woman in the water. It is believed the woman jumped from the wharf.

NSW Police arrest a man after breaking up the brawl. ( ABC News )

The woman was helped from the water and taken to hospital for assessment.

Police said as a result of that incident, a fight broke out on board the boat in which several people were assaulted.

One woman was taken to hospital with a "minor bruising" on her arm.

Six people were arrested and taken to Day Street Police Station and charged.

A 25-year-old woman was charged with assaulting police and resisting police while another woman, also 25, was charged with hindering police.

Another woman, 23, was charged with assault.

A 23-year-old woman, 24-year-old man and 26-year-old man were charged with affray.

The six will all appear at Downing Centre Local Court on March 14.

The incident continues a month of drama on the state's waters.

On February 11, a P&O cruise ship had to return to port in Sydney after an alleged brawl over a toilet queue.

Later that week, the Carnival Legend cruise ship made an unscheduled stop in Eden, on the NSW south coast, to evict nine men and male teenagers from one family after several days of fighting.