10 June 2011 Last updated at 07:37 ET

Leatherback turtle seen in The Minch off Western Isles

The turtle was photographed by researchers and volunteers aboard the Silurian

A leatherback turtle has been spotted in the sea off Scotland.

Crew members of the Hebridean Whale and Dolphin Trust research vessel Silurian estimated it was about 1.5m (5ft) long.

They saw the turtle in The Minch, a stretch of water between the Western Isles and mainland Scotland on Sunday.

Leatherbacks nest in the tropics but have been spotted previously off the UK, with one sighting made near a beach at Cleveleys in Lancashire last June.

Dave Hanna, skipper of the Silurian, said seeing the turtle was the most exciting moment of his life.

The cold

The leatherback is the world's biggest turtle and listed as Critically Endangered, largely because of poaching for eggs and snaring in fishing gear.

Typically between 1m and 2m long, the animals weigh up to three-quarters of a tonne and can swim across entire oceans, returning to their ancestral nesting sites to breed every few years.

In 2002, a rare green turtle was found dead off Loch Inver on the north west coast of Scotland.

At the time it was believed to be only the third recorded discovery of a green turtle in Scottish waters in more than 150 years.

The animal normally lives in tropical and sub-tropical waters and scientists said it probably perished in the cold after losing its way.