[1] According to Feijoo, legend has it that around 1650 there lived in Liérganes, a small village in Cantabria, northern Spain, a couple named Francisco de la Vega and María del Casar.

[2] However, five years later, in 1679, while some fishers were seafaring in the Bay of Cadiz, in southern Spain, they noticed that a strange-looking creature had become entangled with their fishing nets, and was trying to fight its way out.

When they got the creature on board, they found that it had indeed a human shape: it looked like a young man, with white skin and thin red hair.

Domingo de la Cantolla, secretary of the Holy Office, confirmed that there was a place called Liérganes near the city of Santander from which he himself came.

From Liérganes came the word that no creature had ever been seen around the town, and that the only extraordinary event that had happened lately was the tragic death of Francisco de la Vega, who was indeed red haired, in Bilbao five years earlier.

He quoted several sources of which, being educated people, he seemed confident enough, including the Marquis of Valbuena (a finely educated nobleman from Santander), don Gaspar Melchor de la Riba Agüero (a knight from the Order of Santiago from Gajano, a town near Liérganes), and don Dionisio Rubalcava from Solares, who allegedly knew and met Francisco de la Vega.

Apparently, Feijoo somehow believed in the existence of fish-men, as he later further extended his views offering a set of scientific arguments backing his claim.