After what must have been a tremendous storm in the fall of 1808, farmer John Peace of the Shetland island of Stronsay noticed a dead animal. It was caught on off shore rocks and the farmer, who was in the process of cleaning up his property after the storm, eventually rowed out to get a closer look.
Farmer Peace at first imagined he had a dead whale to contend with. Once he got to the already decomposing carcass, however, he thought differently. As he later described it, the creature had a long neck with an unusually small head atop it. It had a thin tail like an eel and two matching fins on either side of it's body. A measurement showed the creature to be over 50 feet in length.
Unfortunately the animal could not be moved but it was closely examined and a drawing was made by a local artist. Notes and the drawing soon came to the attention of noted naturalist Patrick Neill. He poured over the facts he had and in November of 1808 he read his paper on the animal to the Wernerian Natural History Society of Edinburgh. Neill concluded that, in his own words:
...no doubt could be entertained that this is the kind of animal described by Johann Remus, Egede and Pontoppidan, but which scientific and systematic naturalists have hitherto rejected as spurious...
In other words the creature was a rare "sea snake" and Neill took it upon himself to name the "new" species Halsydrus or sea water snake. So it stood in naturalist circles for almost one hundred and fifty years.
After World War II another native of Scotland, writer and scientist Gavin Maxwell, took up the case of Halsydrus. Maxwell was a big fan of the basking shark (shown above) and he had a hunch. The basking shark, it seems, is one of the largest proper fish in the world with modern specimens recorded up to 40 feet long. They strain their plankton food through a long set of gill arches and they are ridiculously common in the cold waters around Scotland and the Shetlands.
Maxwell finally came to the conclusion that Neill's Halsydrus was in fact a basking shark in the advanced stages of decomposition. The picture drawn from life did not show a head but a skull, and the gill arches give the erroneous appearance of an elongated neck. The cartilage that replaces bone in a shark's body would collapse quickly, giving the tail a more sinuous, eel-like look but the thick fins would remain in tact for some time. Essentially, Maxwell busted Neill's Halsydrus myth.
In a way it's sad, despite the strictly scientific correctness of it. I like imagining unknown animals beneath the sea foam. Fortunately neither naturalist Neill nor farmer Peace ever found out they were wrong.