A person has been taken to hospital after being swept out to sea in the freak swells on Wellington's south coast.

A Wellington Free Ambulance said the patient was in a moderate condition after being "swept out into the water".

Five homes have been evacuated and the public have been warned to stay away as large swells crash over the road and footpaths between Breaker and Owhiro Bays.

Huge swells rolling into Owhiro Bay on Wellington's South coast, causing extensive damage to roads and vehicles, on Day 21 of the Covid-19 coronavirus lockdown. Photo / Mark Mitchell

A police spokeswoman reminded residents lockdown restrictions still applied.

"If evacuation is required, police will come to your property and speak with you," she said.

"Emergency services have the situation in hand and do not require offers of accommodation for those currently evacuated."

She urged people to stay home and not come to take photos or look at the damage.

A Fire and Emergency shift manager said firefighters were helping police protect the area and evacuate residents.

Police said a shipping container was also floating in Owhiro Bay.

Police have received multiple reports of large waves causing flooding from about 9.50 this morning, a spokeswoman said.

The swells were expected to peak at midday at 6 metres, "which is really quite high".

A worker attempting to clear debris dumped by huge swells rolling into Owhiro Bay on Wellington's South coast. Photo / Mark Mitchell

Dramatic video posted on social media shows large waves pouring on to the footpaths and roads in Owhiro Bay.

Another video shows the Bluebridge ferry pushing through big seas.

Weather in the capital couldn't be nicer - sunshine and light breezes - but the waves were being pushed by forces further away from the country, MetService meteorologist Andy Best said.

MetService shared an animation on Twitter showing heavy swells moving up the East Coast yesterday and this morning. The swells are the reason behind the large waves.

The swells are forecast to move northeast and away from New Zealand tomorrow.

"There may be a tropical cyclone a long way away from Aotearoa and we may not see any impact with the winds, but sometimes we'll see an impact with the swells," he said.

Swells like these happened "from time to time" but "not every year".

"Everything needs to be right, the direction of the flow, direction of the swell."

He warned locals not to go out to see it.

"Absolutely not . . . stay away."

Wellington City Council has closed most of the road between the two bays to protect motorists from debris being thrown on to the road.

Motorists and pedestrians are asked to avoid the south coast and stay safe at home.

High tide was at 11am.

Resident Angela McKeefry said she had seen "lots of water going over the road" throughout the morning, and said it had been "in quite a few front yards".

Waves had ripped a fence off someone's yard and had swept buoys and fishing nets from people's properties into the sea.

A fence from a bridge over the Owhiro stream was "draped across the road and across the beach".

At one point McKeefry saw a wave crash "at window height" over three cars parked outside people's houses.

She said it was "the most exciting thing that's happened since lockdown".

"It's a mess and I would hate to be down there."

The swell has been hitting the south coast through the night.

Christine Ea said she was having coffee with her family and commenting on how high the water was, "then the wave just crashed up and poured on to the roads".

"We've seen waves like this around Petone and Eastbourne and in Island Bay on a few occasions but no waves this high in Owhiro Bay," she said.

"The size of the waves are increasing and it's getting into the houses at the end of the bay. Even our skip bin is moving."

Susie Jones lives on a cliff above the bay and has a "great view" of the scene.

"It had been a very noisy night with the waves coming in," she said.

In the morning they saw waves crashing over the carpark, and then as the tide continued to rise the waves began coming across the road.

Jones said motorists and dog-walkers continued to come around the corner, oblivious to the mess that awaited them.

"We saw a lady have to jump up with her dog to avoid being swept away.

"We couldn't stop people from coming. They couldn't have seen what the danger was from where they were coming from."

Jones said the road was "strewn with branches and detritus from the beach".

"We were worried that people were going to be swept away or hit by big logs that were in the water."

She felt for the people whose homes may have been flooded, saying it was "the last thing that they need".