A YEAR-LONG research project into one of the great mysteries of the sea - giant methane bubbles which can sink ships within seconds - will be aired in the New Year.

The new Savage Planet programme, made with the help of North-East experts, examines the case of a sunken trawler found in an area of sea called Witch Ground, in the North Sea off Aberdeen.

More than a year after it was discovered, researchers are still baffled by the identity of the vessel which suffered very little damage as it dropped like a stone to a seabed riddled with pockmarks from escaping gas.

The trawler, found in an unusually large pockmark known as Witch's Hole, is believed to have been sunk by a massive and very sudden release of methane gas.

The phenomenon has been used to explain the Bermuda Triangle - the area of the North Atlantic in which scores of ships and planes have been lost.

When methane, or natural gas, bubbles through the sea in high enough volumes, it lowers the density of the water to a point at which most objects, including ships, will no longer float.

A vessel unlucky enough to sail over such a methane blow-out would sink in a matter of seconds.

Marine geologist Alan Judd, of Sunderland University, who led the expedition, said: "Any ship caught above would sink as if it was in a lift shaft.

"Even sailors who jumped overboard wearing lifejackets would sink like stones."

He added: "For a boat to have randomly landed within Witch's Hole would be an amazing coincidence.

"Although it is 100m across, it represents a tiny target in the whole of Witch Ground."

Dr Judd said he had met people who had been on ships that had encountered gas and lost some buoyancy.

He said: "It wasn't enough to sink them, but the ship dropped a metre or two, which must have been an interesting experience."

Mr Judd said pockmarks had been occurring for about 10,000 years and were concentrated in Scottish and Irish waters, though gas escapes were unlikely off the North-East coastline.

He began to wonder if the area's reputation for treacherous waters could be caused by methane blow-outs after oil companies surveyed the Witch Ground in the 1970s.

When he persuaded Total, the French oil company, to take a closer look in 1987, the probe hit something solid above the vent, indicating the presence of a wreck.

It was November last year when he returned to Witch's Hole, accompanied by a crew from Granada's Savage Planet series, when the mystery wreck was found.

The search for the identity of the vessel has been spearheaded by marine historian Dr Robert Prescott, of St Andrews University.

"We have searched through ship records, court proceedings indicating loss of life and insurance records, and are no nearer to identifying the trawler," said Dr Prescott.

"One thing we have been able to do is to narrow the age of the fishing vessel to the first 25 years of the 20th Century."

Savage Planet, produced by Granada, is scheduled to be broadcast by ITV in mid February.