A sewage main in the marina car park was damaged during excavation works before 8am and began leaking into the harbour. Beaches from the marina to Fly Point, including SPLASH Waterpark were quickly closed to swimmers.

Hunter Water says crews were on site within 20 minutes and managed to stop the flow of sewage and have the main repaired by 11.45am. Up to 225 kilolitres of sewage was estimated to have leaked.

They then got to work to clean up the site and take samples of the contaminated water.

The incident unfortunately occurred on what was warm, sunny day in the busy school holiday period.

SPLASH Waterpark had been booked out for several days leading up to the leak, with 65 people per hour session from 10am-5pm.

Lifeguard Indi Kelly said she had not experienced anything like it in the five years she had worked at the park.

"It's been a hectic morning letting people know," she said. "It's very disappointing, but it is what it is."

But Ms Kelly didn't think the incident would affect trade too much long term.

"A lot of people have been rescheduling bookings hoping to get back in later in the week," she said.

Frank Future from Imagine Cruises said the sewage smell was "awful".

"I was 200 metres away and the smell was overpowering," he said. "It would normally be packed down there."

Port Stephens Council will provide an update on the situation on Tuesday morning.

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