Three boaties plucked out of the Firth of Thames after their vessel capsized overnight had spent up to eight hours in the water before being rescued.

Their 16ft tinny capsized in the waters just off Kaiaua in the Coromandel and were located by the Auckland Westpac Rescue Helicopter shortly after 1am this morning.

The vessel capsized after the three boaties attempted to clear a rope tangled in the boat's propeller. Photo: Supplied

Only two of the three men were wearing lifejackets at the time and all were starting to be effected by the onset of hypothermia when they were retrieved from the water.

Coastguard Northern Region spokesperson Georgie Smith understands that as they were returning to shore a rope from the vessel got caught around the propeller.

'While they worked to free the rope from the propeller the vessel turned side onto the waves where it then capsized.

'At 11.58pm last night Coastguard's Operations Centre received a call from a wife concerned that her husband had not returned from a fishing trip with two friends out from the Kaiaua Camping Groud near the Firth of Thames.”

Georgie says the family raised the alarm after checking the boat ramp only to discover the men's vehicle still parked up.

The Auckland Westpac Rescue Helicopter was tasked to conduct a search of the area, discovering an upturned vessel matching the tinny's description with three people clinging to the hull at 1.14am.

But the crew were unable to winch the men to safety, resulting in Thames Coastguard volunteers being tasked to head out to the coordinates provided by the helicopter, says Georgie.

'Thames rescue arrived on scene shortly after 2am to find all three persons clinging together with one in the water trying to keep warm.”

Once on-board the men were assessed by Coastguard volunteers who quickly provided them with blankets to get warm and then transported them to at awaiting ambulance at the opu Boat Ramp.

They were then taken to Thames Hospital for observation before being released mid-morning today.

Thames Rescue volunteer skipper Alan Benson is paying credit to the men for keeping together with the safety line they made out of the rope around the propeller.

'This played a big part in that and quite possibly saving their lives,” says Alan. 'They were very fortunate we got to them when we did as hypothermia was starting to kick in.”

Georgie says all three remain incredible grateful for the search and rescue effort and the Coastguard volunteers on-board Thames Rescue for their efforts.

Lion Foundation Rescue was also tasked from Auckland and arrived to secure the capsized vessel.

EARLIER:

Three boaties had a lucky escape after their vessel capsized in the Firth of Thames near Kaiaua overnight.

Following an aerial search conducted by the Auckland Westpac Rescue Helicopter the men were pulled from the water by Thames Coastguard volunteers this morning, shortly after 1am.

When volunteers arrived at the capsized vessel they discovered two men men wearing lifejackets clinging to the hull, while the third - who was not wearing a lifejacket - on top of the hull.

A Coastguard Northern Region spokesperson says its operations centre received a call from the wife of one of the boaties shortly before midnight to report her husband was overdue arriving home.

'The trio were heading home last night when their propeller fouled on a rope,” says the spokesperson. 'On attempting to clear it the vessel capsized.

'Quick thinking saw them create a safety line for themselves with the rope which may have saved their lives.”

After being plucked from the water by Thames Rescue the three men were transported to a waiting ambulance at the Kopu Boat Ramp.

They were taken to Thames Hospital for observation overnight and were released this morning with a clean bill of health.

'This was a great effort from Coastguard volunteers who were paged from their homes to attend and our team in the operations centre,” says Coastguard.