Wellington weather: Wild waves smash ferry during sailing

An Interislander ferry was hammered by waves this morning as it navigated the Cook Strait before sailings were canned for the rest of the day.

A person onboard the Interislander captured part of the dramatic journey.

Video footage showed waves crashing over the side and rolling towards the door of the vessel - forcing the person filming to quickly slam the door shut.

The ferry was one of the only ones which departed from Wellington this morning, heading into forecast swells of up to 7m.

The person said it left for Picton at about 9.30am when conditions were windy but reasonably calm.

"It felt like the calm before the storm," they said.

The journey started getting bumpy before the ferry had even left the harbour.

About 45 minutes after they set sail waves were "hammering down", the person said.

"It was super-duper rough. I was in my cabin and things were falling over and there were a few times when I had to hold on to the railing to keep myself up.

"There were times when you felt like you were getting pushed down into the deck and other times when you could jump and float up."

The person said there were bound to be a few sick people and imagined everyone would have been quite relieved when the ferry made it to Picton at 2pm.

Interislander executive general manager Walter Rushbrook said those booked onboard the company's ferry, Kaitaki, had been advised of bad weather and give the opportunity to cancel or rebook at no cost.

"Kaitaki had a bumpy Cook Strait crossing today.

"Our ships are designed for rough weather and we always treat safety as our top priority. In conditions like this our main concern is the comfort of the passengers.

Rushbrook said other sailings during the day were cancelled and affected passengers were rebooked on Friday sailings.

Earlier today a Bluebridge ferry tried to leave at 8.15am, also hoping to make it out before the storm hit.

However, the weather deteriorated faster than expected, and the ship returned to port before it made it out of the harbour.

A spokesperson for the ferry said safety was the company's biggest priority and conditions in Cook Strait made it unsuitable to sail.

"We're sorry that this will inconvenience our customers, and we're working hard to get everyone across Cook Strait as soon as conditions allow."

Anyone who wished to cancel their sailing would be refunded.

It's been a wild morning for the capital with gale-force winds tearing off roofs and grounding all flights in or out of Wellington.

Several roads have been closed across the region, and hundreds of homes are without power as the storm rages on.

A heavy swell warning is in place for Wellington from Cape Terawhiti to Turakirae Head. Swells are expected to peak at 7m early this evening, and will be between 5m and 7m through tomorrow afternoon.

Wellington Regional Emergency Management is warning people to stay off the beaches and avoid driving on coastal roads during peak swells.

"Swells can cause surface flooding and debris wash up including driftwood, seaweed, sand and gravel."