A kayaker was left exhausted and suffering from mild hypothermia after getting into trouble while fishing at Waikawau in the Coromandel.

The man, who is in his 50s, toppled out of his kayak when trying to pull up his anchor and was unable to get back in.

A member of the public on the shore spotted him through binoculars and alerted emergency services.

Auckland's Westpac Rescue Helicopter was called out just after 10am.

The man had been struggling in the water for around an hour when a passing boat, on its way back from fishing, pulled him out of the water.

The kayaker was well prepared - he was wearing a life jacket and had been carrying a radio, but this dropped into the water when he fell in.

He was flown to Thames Hospital in a serious condition.