HMS Daedalus sea serpent: Captain M'Quhae's report and the Richard Owen dispute, 1848

HMS Daedalus was a Leda-class frigate built at Sheerness. In the summer of 1848 she was homeward bound from the East Indies, by way of the Cape and St Helena. Sunday 6 August 1848, about 5 p.m. The ship stood at 24°44′S, 9°22′E, some 300 miles off present-day Namibia. The weather was dark and cloudy, with a long ocean swell running.

Midshipman Sartoris saw it first. Something very unusual, rapidly approaching the ship from before the beam. Seven men watched it in all: Captain Peter M'Quhae, Lieutenant Edgar Drummond, the master William Barrett, Sartoris, the quartermaster, the boatswain's mate and the man at the wheel.

M'Quhae called it "an enormous serpent, with head and shoulders kept about four feet constantly above the surface of the sea." Judged against the main-topsail yard, at least sixty feet of the animal lay along the surface. Its head was "without any doubt, that of a snake." It was dark brown, yellowish white about the throat. It had no fins, "but something like the mane of a horse, or rather a bunch of sea-weed, washed about its back."

It showed no undulation. It never left its course to the south-west. It passed so close under the lee quarter that, the captain wrote, "had it been a man of my acquaintance I should have easily have recognised his features with the naked eye." For twenty minutes it stayed in sight of their glasses.

Drummond's journal tells it a little differently. A head about ten feet long, "long, pointed, and flattened at the top." A back fin perhaps twenty feet behind it. A distance of perhaps 100 yards.

The story reached The Times in October 1848. The Admiralty asked M'Quhae to confirm it, and his report, dated Hamoaze, 11 October, did exactly that. On 28 October the Illustrated London News printed it with engravings drawn with his input. About 275 items followed in British and Irish papers.

Then the anatomist Richard Owen stepped in. It was an elephant seal, he argued, and the supposed tail was only its eddy. M'Quhae rejected this outright. It was "neither a whale, a grampus, a great shark, an alligator," he replied, nor "a common seal nor a sea-elephant." In 1858 an anonymous officer of the Daedalus wrote to The Times. It was, he insisted, "beyond all question a living creature."

The theories kept coming: a long-bodied shark, a surviving plesiosaur, an oarfish, or floating seaweed. In 1883 Henry Lee proposed a giant squid swimming at the surface. In 2015 Gary J. Galbreath of Northwestern University and the Field Museum made the case in the Skeptical Inquirer for a sei whale skim-feeding at the surface.

Seen side-on, its raised upper jaw and flat head can look like a reptile's. Its whitish baleen matches the pale throat. The ridge down its head explains the mane. Drummond's back fin fits its dorsal fin. Galbreath trusted Drummond's own 1848 sketches over the later engravings, and noted that 100 yards in squally weather sits uneasily with recognising a face.

Nobody has ever accused M'Quhae or his officers of inventing what they saw. The only hoax in the story is a separate one, a faked follow-up sighting known as the Mary Ann letter. The argument was always about what the Daedalus crew saw, never whether they saw it. The writer Phil Robinson called the record "above all others."