If it was caught in the gas it would have been swamped and gone down as though it were in a lift

Alan Judd, Sunderland University

The wreck, which has just been surveyed by submersible camera equipment, lies in an area known as the Witch's Hole, 150 kilometres north east of Aberdeen.

The patch of seabed, at least 100 metres across, is one of many "pockmarks" in the region - depressions in the sediments created by escaping gas.

That the boat should be sitting upright in the middle of this "crater" could be just a huge coincidence, but marine geologist Alan Judd told BBC News Online it was also possible the trawler was in the wrong place at the wrong time.

The Skandi Inspector has the expertise to survey the seafloor

"Was it just happenstance that it landed here or, against even longer odds, was it sailing immediately above the Witch's Hole when there was a gas escape? If it was caught in the gas it would have been swamped and gone down as though it were in a lift."

'Shallow gas'

Organic matter deep under the seabed generates methane which works its way up through the sediment over thousands of years. Pockets of gas can build up just beneath the seafloor and are held in place by the weight of overlying grains of sediment and the column of water.

Robotic camera equipment was sent down to look at the trawler

Every once in a while, the pressure of the gas increases to such a level that the methane bursts out and streams to the sea surface.

Oil drilling platforms are well aware of the dangers of this "shallow gas" phenomenon and have safety procedures to follow if they hit a methane pocket. But there are no confirmed reports of ships being caught out by sudden and large releases of gas.

The expedition to the Witch's Hole wreck was filmed by the Granada TV programme Savage Planet using the expertise and equipment of the offshore survey ship Skandi Inspector, operated by Fugro-UDI.

Although pictures from a robot submarine showed that the sunken trawler had indeed suffered little damage and gone straight down, there was nothing Alan Judd saw that proved the gas hypothesis.

I think most ships are lost through stress of weather but the argument that it was lost in a gas emission is a plausible one

Dr Robert Prescott, St Andrews University

"It's an early 20th century steel-built steam trawler. That much is clear from the pictures - the configuration of the deck, the layout of hatches, the shape of the hull," he told BBC News Online.

"I think most ships are lost through stress of weather but the argument that it was lost in a gas emission is a plausible one. It's an intriguing hypothesis and I keep an open mind on it."

The findings of the institute's research on the wreck will be revealed in the Savage Planet programme due to air early next year on ITV. And a more detailed account of the recent expedition can be found on the New Scientist website. The magazine travelled on the Skandi Inspector.