"The weather was quite rough - there were some strong winds," he said. "If those guys hadn't been watching through their telescope, it could have been a different story."
Wairarapa Search and Rescue senior constable Tony Matheson said the divers were amazed at the quick response time of their cray fishing rescuers.
"That area is pretty isolated - so they thought nobody would have been aware their boat had tipped," said Mr Matheson.
"There are definite risk factors with the coast - because of where it is, it can be a problem getting rescuers out there quickly.
"If it's too windy, the rescue helicopter won't be able to make it out there."
When it capsized, the boat was at anchor, about 100m off shore.
At the time, there were strong norwesterly wind gusts, reaching about 25km/h.
As they were closer to the shore, the men were reasonably sheltered - but sea conditions on the coast can change rapidly, said Mr Matheson.
"It was good the rescue boats moved as fast as they did."
Mr Mackay said a police helicopter was "on standby" to respond, but it was unable to take off due to wind conditions in Wellington.
It is believed the rear anchor rope got tangled around the outboard motor, thus unbalancing the boat and making it more vulnerable to tipping.
Mr Matheson said the four men were from Masterton, and were experienced paua divers who knew the coastline well.
In fact, Mr Mackay received a report that they continued diving as the rescue boats approached.
While the men were delighted to be back on land, they had to leave the fruits of that day's labour behind.
