A fisherman who clung to a floating petrol container for seven hours after his boat capsized has been plucked to safety by Coastguard.

Two men were fishing at Waihi last night when their boat upturned.

One man swam to shore to call for help while the other clung for life to a yellow 20-litre petrol container, waiting seven hours before he was rescued.

The boat was spotted at 6.20am by Auckland Westpac Rescue Helicopter, and the stricken man was discovered about 200m from the vessel and returned to Waihi for medical assistance.

Two men were fishing at Waihi early this morning when their boat upturned. Photo / Supplied
Two men were fishing at Waihi early this morning when their boat upturned. Photo / Supplied

The Auckland Westpac Rescue Helicopter received a call about the missing fishermen from Waikato SAR Police at 5.30am.

"Reports were of two men whose 7m boat had upturned. One man had swum to shore to alert emergency services."

Westpac Rescue 1 took off from Coromandel Rescue Helicopter Trust (CRHT) at Whitianga for the search. The upturned vessel was located at 6.20am and Coastguard Waihi was advised of the GPS location and vessels called in.

"A man in the water was sighted approximately 200m from the boat. Coastguard vessels retrieved the man who was clinging to a yellow 20 litre petrol container for seven hours."

The man, in his late 40s, along with the upturned vessel, was safely returned to Waihi for medical assistance.

After his lengthy spell in the water the fisherman was lifted by helicopter and taken to Thames Hospital.

The rescue helicopter crew used night-vision goggles to try and track the fisherman down.

A Coastguard spokeswoman said the fishermen failed to log a bar crossing with Coastguard, which would have helped them launch the rescue effort sooner.

"It would have prevented the fisherman having to be in the water for so long."

Coastguard Waihi Beach skipper Tim Watts said the fisherman stuck out at sea was not wearing a lifejacket, although there were some on board the boat.

"He had mild hypothermia ... he was very pleased to see us."

Mr Watts said the fisherman tipped over on a bar about 11pm last night.

"One of them got to shore around 3am to raise the alarm.

"The conditions were not ideal for what they were doing, and their skill level was not up to scratch."