Cool temperatures quickly land overboard boaties in hot water

Remarkably low sea temperatures this month have prompted the Coastguard to issue a warning about hypothermia.

Within just a few days, three people have been rescued with hypothermia, despite the fact that all wore wetsuits and had been in the water only briefly.

Coastguard operations director Dean Lawrence said hypothermia in such cases was unusual for this time of year.

"It just raised a bit of a warning flag to us," he said.

"People think it is Christmas in a week - that it is summer. But maybe it is not summer."

In the first incident, a windsurfer near Auckland's Eastern Beach was rescued on December 5 after his mast broke.

He was seen sitting on his board and holding on to a mooring buoy, waving to shore for help.

When the Coastguard responded he had been towed ashore by a jetski. Once on the beach he collapsed with early effects of hypothermia.

"The person did not know he was suffering from hypothermia and said he was okay. But then he collapsed."

Five days later, two jet skiers with mechanical problems about 500m from Mairangi Bay had severe hypothermia.

Their condition was a concern, so the Coastguard sent an ambulance.

However, they did not need to be hospitalised.

Mr Lawrence said the problem was low ocean temperatures for the time of year.

MetService records the temperatures at 16C in the Hauraki Gulf - 2C cooler than usual.

He said it was always better for people on shore who saw others in trouble on the water to call the Coastguard too early rather than too late.

The Coastguard would rather attend an incident early than later when the situation was serious.

Hypothermia crept up on people and could set in within about 20 minutes, depending on the circumstances.

"People have to appreciate that we are not in the tropics and they have to appreciate that the wind can play a significant part as well."

* Throughout the summer season, the Herald will highlight stories of the Coastguard and the work it does.