An investigation has been launched after a man died in a diving incident off the coast of Lowestoft.

Coastguards were alerted by the operator of the Raider V dive boat 17 miles off the coast yesterday afternoon after reports that a diver had died.

It is understood that the diver had gone down about 17 metres, when he became unwell and had to make an emergency ascent.

When the diver returned to the surface he was given emergency CPR and a RAF search and rescue helicopter from Wattisham called to airlift him to the James Paget University Hospital at Gorleston. He was pronounced dead upon arrival at hospital.

His death is currently being treated as unexplained.

Seven people were on board the dive boat at the time of the incident, which was on a recreational trip, that had set off from Lowestoft at about 10am yesterday.

A second diver who was on the boat was also taken to hospital with suspected decompression sickness and was taken to land by Gorleston Lifeboat.

A spokesman for Norfolk Police and Suffolk Police, said: 'The second diver was brought ashore at Gorleston and was also taken to the James Paget Hospital where he was medically assessed. He is likely to be discharged this evening [Friday].'

'The diver that died is not thought to be local and, as is standard procedure, his death is currently being treated as unexplained.'

A spokesman for Humber Coastguard said the Gorleston Lifeboat was called at about 1.20pm and arrived at the scene of the incident by 2pm.

'It was a dive boat and one of the divers had suffered some sort of fatality, but we do not know what at this stage. It looks like he might have had some form of medical condition,' the spokesman said.

Police officers attended Hamilton Docks in Lowestoft to meet the dive boat, that docked around 6.30pm, and enquiries are being made into exactly what happened.

Police are working with the coastguard and liaising with the Health and Safety Executive following the incident.

A spokesman for Lowestoft Lifeboat said that recreational diving was popular locally, with most of the dive clubs understood to head to north Norfolk to dive on the many old wrecks there - where 'the water off that part of the coast was a lot clearer.'

The spokesman said: 'There are a couple of dive boats that regularly operate from Lowestoft.'