A local couple used their boat to ferry police to the fishermen and officers pulled the pair from the water.
"By this time it was dark and the weather was extremely rough, and without the quick response from police and locals the outcome could have been tragic," police said.
"The pair were returned to land and treated by ambulance for hypothermia."
"This is the second water rescue in the Firth of Thames this week and a timely reminder to make sure you are ready and equipped for emergencies when out on the water."
Last Saturday night, four boaties stranded in the water without lifejackets after their boat sank were winched to safety by the Auckland Westpac Rescue Helicopter.
The three men and one woman, aged in their 20s and 30s, were all saved and none needed to go to hospital.
However, rescue chopper co-pilot Simon Owen told the Herald that had they taken a couple of minutes longer to pluck the cold, shaken and distressed woman from the sea, she could have been dead.
Police yesterday released gripping video of the rescue along with a recording of the emergency call made by one of the group.
The footage shows one of the men urging the police to send help immediately because they were about to lose the phone.
"We don't have any lifejackets and we're hanging on to a cushion," one yells.
The call ends abruptly with the sound of the phone disappearing under water.
The group were then spotted by the police Eagle helicopter and one officer jumping out of the chopper to carry lifesaving flotation equipment to the boaties.
The officer even handed over his own lifejacket to one of the boaties as there were not enough to go around.
Then the rescue helicopter arrived to winch them to safety.
Maritime NZ deputy compliance manager North Jason Lunjevich said his team were investigating Saturday's rescue and consulting with police and Coastguard NZ.
"Our investigation will involve interviewing those involved," he said.
"We will assess the information gathered and decide the next steps."
Police said the two fishermen involved in yesterday's rescue had been wearing lifejackets and had appropriate emergency kit.
"The rescued pair had reflective patches on their life jackets and emergency whistles, which played a major part in officers being able to spot them quickly and get them out of the cold water," police said.
They reminded all boaties to:
• always wear a life jacket when boating, jet skiing or using other craft on the water
• have two forms of waterproof communication on board
• make sure equipment is safe and working
• leave trip intentions with someone onshore
• always check the water and weather forecast
