UPDATED: 2.25pm: A commercial diver brought in by Waikato Regional Council has successfully plugged the diesel leak from a sunken boat in Coromandel Harbour.

Duty regional on scene commander Adam Munro this is good news for nearby oyster farms and the environment generally.

Windy Point. Photo: Google Earth

'We decided to bring in the diver promptly this morning to help avert the risk to the farms and other parts of the marine environment.”

But it is unclear exactly how much diesel has spilled from the 12-metre private boat's fuel tanks, although there has been a relatively substantial surface slick in the harbour.

It is also unclear at this stage what, if any, damage there has been to the marine environment.

As a precaution, two oyster farms have suspended harvesting due today because of the spill after being advised of the leak by the council.

But Adam says diesel is a light fuel and breaks down rapidly when exposed to the air and choppy sea conditions.

'Diesel has a lower rate of staying around in the environment than heavier fuel oils so we expect most of it to break up over the next 24-48 hours.

'We will continue working with the very co-operative owner and the oyster farm operators to manage the situation going forward.

Adam says they will continue monitoring the harbour today and over the weekend.

The owner's insurer has dispatched a boat from Auckland and an attempt will be made to re-float and salvage the sunken vessel this afternoon.

This morning the council's Coromandel harbour master put booms around the boat to help prevent diesel from spreading while council dispatched other gear and staff to the scene.

The boat sank on its mooring some time overnight in Waipapa Bay off Windy Point. The sinking was in 4.5 metres of water and the boat had approximately 400 litres of diesel on board.

Adam says the cause of the sinking is yet to be determined but the owner was helping with council's investigation.

'As a general comment, any boat sinking like this is a timely reminder of the need for owners to moor their boats safely and to keep them well-maintained.

'This is particularly important in areas where sensitive sites such as marine farms are present.”

EARLIER:

UPDATED 11am: The Waikato Regional Council says a commercial diver will plug the leak of diesel coming from a sunken private vessel in Coromandel Harbour.

As marine oil spill response staff work to limit the impact of the spill, two local oyster farms have decided to defer harvesting due today as a result of the spill.

The council's harbour master deployed spill containing booms around the vessel after learning of the sinking early this morning. Other specialist gear and staff are being deployed as well by the council.

The vessel owner's insurer is arranging salvage and it is hoped to have the boat re-floated by this afternoon.

Duty regional on scene commander Adam Munro says his team have had good co-operation from the owner and their insurer and affected parties have been notified.

Adam stresses the cause of the sinking is yet to be determined.

The boat sank on its mooring in 4.5 metres of water some time overnight in Waipapa Bay off Windy Point.

The boat had approximately 400 litres of diesel on board.

'Our current focus is on containing the leak of the diesel to help keep it away from sensitive areas and protect the marine environment,” says Adam.

EARLIER:

The Waikato Regional Council marine oil spill response staff are working to contain a diesel leak after a boat sinking in Coromandel Harbour overnight.

The local harbour master has deployed sorbent booms around a 12-metre vessel to help prevent the diesel spreading, with further gear and specialist staff currently being sent to the scene.

Approximately 400 litres of diesel was on board the vessel which sunk on its mooring for unknown reasons in 4.5 metres of water, several hundred metres off Windy Point.

Duty regional on scene commander Adam Munro says they are currently working to contain the leak.

'Our current focus is on containing the leak of the diesel to help keep it away from sensitive areas and protect the marine environment.

'We are working closely with the vessel's owner, who will be arranging salvage through their insurer.”

Courtesy of Google Maps