Six Shetland fishermen catch a "mermaid" on their lines off Yell

July 1833. Six fishermen were at sea off the Isle of Yell, in Shetland's North Isles. No source records the day, the fishing ground or the men's names. Only that one of them was the skipper. Then they drew in their lines. Something was tangled in them.

It was about three feet long. The upper part of its body resembled a human's, "with protuberant mammae, like a woman." The face, the forehead and the neck were short, "resembling those of a monkey." Its small arms were kept folded across its breast. The fingers were distinct, not webbed. A few stiff, long bristles ran from the top of its head down to its shoulders, and it could erect and depress them at pleasure, "something like a crest." Below, the body was like a fish. The skin was smooth, and grey.

It did not fight. It "offered no resistance, nor attempted to bite, but uttered a low, plaintive sound." One modern retelling puts it more simply. She moaned piteously.

The men kept it in the boat for about three hours. Then they untangled it and put it back into the sea. It "instantly dived, descending in a perpendicular direction." No specimen was kept. No drawing was made. Karl Shuker, who revived the case, suggests superstition outweighed any wish to bring it ashore.

The skipper told the story to a Mr Edmonston, described as "a well-known and intelligent observer". Edmonston passed it on to the Professor of Natural History in the University of Edinburgh. The professor stood by the crew. "Not one of the six men dreamed of a doubt of its being a mermaid," ran his defence. The mermaid, he noted, "is not an object of terror to fishermen, it is rather a welcome guest." Then the line most often quoted: "It is quite impossible that six Shetland fishermen could commit such a mistake." Some retellings give that line to Edmonston instead.

The account reached print through Dr Robert Hamilton, in his 1839 volume Amphibious Carnivora. Modern write-ups sometimes call Hamilton the professor himself, which may merge two different men. Edmonston may have been Laurence Edmondston of Unst, a Shetland naturalist. That link is unproven. One web source even dates the letter to 1823, in the Edinburgh Magazine. The two dates have never been reconciled.

The professor's insistence tells its own story. Even then, someone had raised the idea of a seal. A small grey animal with a short face, a mournful cry and a straight dive would fit a young seal. Yet no commentator has explained the separate fingers, the folded arms or the crest that rose and fell.

In Sea Fables Explained (1883), Henry Lee argued that mermaid reports in general came from manatees and dugongs. Whether he ever addressed the Yell catch is unclear.

In 2012 Karl Shuker gave the creature a name of its own. The Mermonkey of Yell. It belongs to a cluster of mermaid reports from the same era, from Caithness in 1809 to Connemara in 1820. Most were glimpses from the shore. This one was hauled aboard, held for three hours, and set free.