Homes, businesses, roads and cycleways were no match for the storm surge that raced into Nelson's shallow bays and inlets like a river in flood.
Ex-tropical cyclone Fehi smashed into much of the south and west of the South Island yesterday, blocking roads, bringing down power lines and causing widespread damage.
As the huge waves clawed at shorelines, and rushed into people's homes, Nelson sailor and charter boat operator Martin Holmes decided to ride out the storm on his boat in the harbour.
He said conditions were like nothing he'd seen before.
"The pressure of the waves under the wharves was like setting off blowholes on the West Coast - there were these geysers surging up from under the wharf.
"Just looking along the waterfront ... the waves were enough to lift those big concrete pads in front of the yacht club and burst through the floor of the other places [The Boatshed Cafe and the Boathouse concert venue]."
People were forced from their homes in Monaco, near Nelson Airport, Ruby Bay in the Tasman District and businesses on Mapua wharf closed when police advised people to leave.
Nelson-Tasman civil defence controller Roger Ball said yesterday's relief efforts have moved up a gear today.
"We've got Urban Search and Rescue, a Red Cross team, council building inspectors and structural engineers, and they're going door-to-door in the affected areas. What we're trying to do is find out where the pain-points are and connect people with those that can help them," Mr Ball said.
The co-owner of a coffee roastery on the Mapua wharf, Ali Slotemaker, said people did not take the storm seriously at first.
She said people on the wharf were getting worried long before high tide.
"The tide was looking high and the surge was quite aggressive, so the police and civil defence cleared the Mapua wharf area by about 11.20am.
"We tried to come back later to get something out of our business and were told we're not allowed in the area."
Ms Slotemaker said the sea stopped just short of their business - set back some distance from the Mapua Channel.
She said if it happened once it could happen again, and it was likely to trigger conversations in the community about future development.
Nelson Mayor Rachel Reese said the city has some serious thinking to do.
"Yesterday we saw a volume, a speed and a power of water that we haven't seen before. I know there's been climate-change sceptics out there - those who ask if it's weather or climate-change.
"But the reality is we are going to see more and more storm surge, and that means we have to think very carefully about our coastal inundation.
"If there's any silver lining that can come out of these dreadful events - if it helps people engage in that conversation then I think that's a good thing."
Roger Ball from Civil Defence said while some losses could be replaced, others cannot be so easily fixed.
The popular Boat Shed Cafe on the Nelson waterfront is at least one business that has shut up shop.
"There's a lot of damage to roading, cycleways and of course there are a lot of properties with water through them, and we have some quite high profile locations that we've lost along Rocks Road (Nelson waterfront), and damage to many other places."
Mr Ball said workers and volunteers would be out helping residents over the weekend.