A southerly swell peaked at more than six metres along the Hunter coast, the result of a deep and complex low-pressure system moving up the NSW coast.

The conditions produced monster surf at some of the region's beaches, most notably at Merewether on Saturday where hundreds of people lined the foreshore to watch only the most experienced of surfers take on huge waves.

Dave Anderson, who produces the Newcastle Herald's daily beach watch report, said the conditions were "the biggest surf we've probably had in a few years" but akin to those encountered "around this time last year".

"I got readings from our Waverider Buoy [on Saturday] ... between 4.8 to 6.8 metres running at 15 seconds, which is quite a mass of water, reading trough to trough," he said of the swell.

"It was basically only Merewether, locally, that anybody managed to get out.

"There wasn't a great deal of people [surfing], it was a very difficult paddle out.

"The wave size was peaking eight to 10-foot plus and breaking way out beyond what we call Third Reef."

Some surfers were being towed onto waves by jet-skis at both Merewether and Caves Beach. Mr Anderson said there had been a "few broken boards" but no injuries were reported.

The Newcastle and Merewether ocean baths were inundated on the high tides, and videos posted on social media showed water crashing through the main pavilion entry at Newcastle into the car park.

Paul Johnson, of the Stockton Landcare Group, said land between Corroba Oval and the beach that volunteers and council contractors had been working to vegetate suffered damage.

"We've been working there for years but all volunteers are in limbo at the moment with COVID-19," he said.

"[The council] has had contractors through there and they've done a terrific job of replanting and mulching, but unfortunately ... the big seas and high tide just went straight across the top.

"Salt water went within 10 metres of Corroba Oval."

Mr Johnson said it was pure "luck" that sections of the beach to the south had managed to escape relatively unscathed compared to previous big-swell events.

"The seas are picking up right now, the wind is picking up right now ... so tonight is going to be interesting," he said on Sunday afternoon.

The Bureau of Meteorology is forecasting the low pressure system to linger offshore for the next few days before its weakens and moves to the east by mid-week.

A hazordous surf warning remains in place for the Hunter coast on Monday.

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