Despite the aquatic ape theory being ignored or deprecated as a pseudoscience by academics and scientists, Marty took it seriously. He published a paper in a special issue of the Journal of Human Evolution in which he argued that the aquatic ape ancestors of modern humans were, in fact, not extinct but had evolved into fully aquatic mammals.

The scientific community’s response was swift and harsh. Biologists, anthropologists, evolutionary theorists, paleoanthropologists, and other experts pounced on the hypothesis, many calling it “crank anthropology” akin to alien-human interbreeding and Bigfoot.

Nevertheless, all publicity is good publicity, as they say, and Marty began packing lecture halls in the UK and US as a guest lecturer, while also conducting interviews on radio stations and podcasts and major television stations.

Within a year, he had become an international name and the face of a newly coined scientific discipline, sirentology—the study of mermaids and mermen, collectively known as merfolk.

In 2017, at the height of Marty’s popularity, a well-respected filmmaker contacted him, claiming to possess video evidence that supported his merfolk theory. Marty was initially skeptical. Despite the filmmaker’s credentials and reputation, the timing of the video evidence (surfacing just as the idea of merfolk was capturing the public’s imagination) seemed too coincidental. Even so, Marty agreed to meet the filmmaker, and when he saw the footage with his own eyes, his skepticism vanished.

The video had been taken just after dawn by an American man walking his dog along a remote stretch of beach in southern California. It began with the man spotting three beached whales (the US Navy had been testing sonar blasts two kilometers off the coast at the time, which were believed to have killed the whales). The man filming the footage was speaking to someone on his phone. His voice rose in excitement as he spotted something farther down the beach. He hurried toward it before slowing to a walk and steadying the camera on a beached bottlenose dolphin.

Partly obscured by its smooth, gray body was some sort of large fish.

The man was about ten meters away from the dolphin and the fish…only the second animal was now clearly no fish, as it had two very distinct arms protruding from its sides. As the man drew closer, the camera revealed more of the bizarre creature. It lay on its chest, facedown. Its head was covered with scraggly black hair. Its tightly muscled upper body resembled a human’s (especially the arms, ending in huge, webbed hands). The skin was a light shade of blue. From the waist down the legs fused into a powerful tail that terminated in a forked fin. This was covered in horny skinfolds like those found on armadillos.

The man closed the final few feet to the creature very slowly. He nudged its shoulder with a toe. It didn’t move. He crouched, panning the camera up and down the thing’s body. He reached a hand under its shoulder. Grunting, he rolled it over onto its back. The face was humanoid…yet horribly different too. There were no eyebrows or facial hair, and the forehead seemed broader than a human’s, the jaw slimmer. The ears and nose were almost non-existent, and the mouth was a lipless slit. The large, wide-spaced eyes, black and pupilless, stared blankly at the camera.