During my studies I’ve been spending a lot of time reading old documents. An account from 1603 popped out at me as it described a relatively unknown creature- the Pendine Mermaid!
In 1603, a man only known as PG sent a letter to his cousin HP describing the curious events which had occurred on the 17th of February near Gylmanes Poynt (now Gilman Point/Pwynt Gilman) in Pendine, Carmarthen in Wales. Following the usual pleasantries, he told an astounding tale.
The tale
At about 3PM, a man named Thomas Raynold was walking the shores of Hollogoho, between Gylmanes Poynt and Tolwen. Near the point he saw a strange figure swimming; a figure so strange and wonderful that he spent nearly two hours observing it.
The figure was a woman from the waist upwards with brown skin, and large white breasts covered with something like a hood which hung around her neck. She had two fair hands, everything a normal woman would have.

Raynold debated telling the people of the town what he had seen, as he imagined that they would be unbelieving without seeing the body themselves. After weighing up his options he sped towards town and brought as many of his neighbours and cousins as he could find back to the point.
The creature was still swimming, and witnesses were able to spend over half an hour observing her. The creature never changed shape. As the tides changed she swam away, making it appear more of a grey colour. The observers noticed that she had ears like those of a hound, yet bigger and shorter. Her back was like a small boat, a yard (3 feet) or more in width. Her tail was 2 fathoms in length (12 feet). She was seen swimming around the area until nightfall, when observers lost sight of her.
She was never seen or heard of again.
Aftermath
The contents of the letter along with an artists rendition was printed as a pamphlet in London titled “A most strange and true report of a monsterous fish, who appeared in the forme of a woman, from her waste vpwards”. It has been suggested that a magistrate local to Pendine named Mr. William Sandars heard of the tale, and carried out his own investigation several weeks after the event- creating the letter. The letter included a list of local witnesses, whose accounts of events may have been used in its creation.
Unfortunately, there do not appear to have been any other sightings of the creature. Some have suggested that the townspeople were confused by a manatee or dugong, which have historically been blamed for alleged mermaid sightings. It seems strange that her hands would have been mentioned so specifically if this were the case. As with most folklore and cryptid related stories, we may never know the truth.
References
Pamphlet with museum notes available on Proquest at: https://www.proquest.com/docview/2240910594/54532354/1090AAB9B4F349CCPQ