In 1808, a large decomposing corpse washed up on Scotland’s Orkney Islands. It was enormous — 55 feet long, including a 15-foot “neck” — and the Royal Museum in Edinburgh decided it must an unknown species of sea serpent.

London anatomist Sir Everard Home later concluded it was a basking shark, but still it’s an enigma — the largest previously recorded basking shark had been 40 feet long.