Lady Elizabeth II rose and rose on a "giant wall on water", killing two of the four police officers on board.
That two survived was thanks to the heroics of a helicopter pilot - who would die in a separate tragedy little more than a year later.
Rod Herd was one of the lucky ones. Twenty-eight years on, he remembers July 2, 1986, well.
Experienced launch master Senior Constable James McLean took Herd, who was then a constable, Senior Sergeant Phillip Ward, and Constable Glenn Hughes on a training run to the harbour heads.
A signalman at Beacon Hill would report southerly gusts of 130kmh and a "big, big swell" at the heads. Waves were peaking at up to 7 metres, Herd said.
The police launch Lady Elizabeth II was handling the waves and McLean was about to take her back in. A Ministry of Transport report would later say the crew noticed a large wave, three waves ahead, coming towards them.
It was probably 7m to 8m high, the report said, though Herd reckons it was even higher.
McLean tried to take the monster wave on the bow. It was probably due to a leading wave having been slowed by water leaving the harbour, causing other waves to join it. Combined, they formed a "giant wall of water" with a breaking crest, Herd said.
The launch went up and up, almost to the crest. McLean gave it more power to try to punch through, but the wave crashed the launch back over on itself.
Herd reckoned it possibly hit the ocean floor, up to 17m below. Water flooded in, forcing him into the "bowels of the vessel". Flailing around "like a dying man grabs at straws", he hit something hard: "I assume it was a body of one of the boys."
As he ran out of air, "the old ‘I'm dying' kicks in", he said, describing it as a peaceful feeling.
He grabbed a ladder he had only recently sanded, and knew where he was. Then he felt carpet above his head and knew the launch was upside down. "That took me back to the world."
Already out of breath, he swam down to get out. He burst through a hole then got caught in rigging, "but I could see light above".
"It was no skill - it was pure luck I got through that hole."
The scene into which he emerged was only slightly less nightmarish than the one below.
The upended launch was thrashing around, the storm was growing, he was injured and covered in blood and - when he eventually clambered to a life ring with McLean - there was no clue as to whether anyone knew of their plight.
But unknown to them, the disaster had been seen from Beacon Hill, above Breaker Bay, and rescuers were on their way by sea and air.
When they heard "that amazing sound of the helicopter" - flown by pilot Terrance Comins, who had diverted from a flight into Wellington Airport, and still had wife Diane on board - "it was the first indicator for us that someone knew our plight. It sort of gave us the will to kick on".
But the helicopter had no gear to attempt a rescue. In storm conditions, it spent 2 hours in the air, directing rescuers, then searching for bodies.
From one crest, Herd spotted a tugboat coming towards them from "way down the harbour" but, a veteran rescuer himself, Herd knew it would be almost impossible to board it.
It was shortly after midday when Herd's friend and partner in numerous other rescues, Peter Button of Capital Helicopters - what is now the Life Flight Trust - appeared overhead.
He knew the helicopter's sound before he saw it and thought, for the first time since the sinking: "I'm going home."
But the howling southerly meant the line with the harness was being blown horizontally. Button lowered the helicopter into shelter between the waves to drop the harness.
AT McLean's insistence, Herd was winched up first. When they were both safely on board, they looked down as the lifeboat they had wished for so much popped to the surface.
Button took them to Wellington Airport, then returned and retrieved Ward's body, which the pair had seen and held for a while as they were in the water.
Even from hospital, they hoped Hughes had somehow got free, and that the fit 28-year-old had swum for shore. But he would be listed as missing, presumed drowned. His body was never found.
Button would win the Queen's Gallantry Award at Government House on November 18, 1987.
Two days later, he was taking a flight with Wellington photographer Ronald Woolf and businessman Dion Savage, when he was diverted to look for an escaped prisoner.
Herd happened to be with Button's son Clive at the hangar when the call came through that the helicopter had hit high-tension wires near Tawa.
Clive Button and Herd raced to the scene, where they heard Peter Button was possibly still alive. Instead, Herd had to help identify the body of the man - "They called him St Peter" - who had saved him just 16 months earlier.
- The Dominion Post
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