Sources : Nereid

Pliny the Elder [1st century CE] (Natural History, Book 9, 4): Pliny 9, 4 The description of the Nereids also is not incorrect, except that their body is bristling with hair even in the parts where they have human shape; for a Nereid has been seen on the same coast, whose mournful song moreover when dying has been heard a long way off by the coast-dwellers; also the Governor of Gaul wrote to the late lamented Augustus that a large number of dead Nereids were to be seen on the shore. - [Rackham translation]

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Marine monsters 6.35): The Nereids are likewise marine beasts, as Pliny says. They are hairy all over the body, and have something of the appearance of a human. When one of these is dying, its groans and lamentations are heard far from its companions, and show that the sorrow of the necessity of death is bitter to mortals. ... We would say that by this the wretched soul is signified, which pretended to bear the likeness of reason with man, but is compelled by the demons to go out in the end of life by the hairs of wickedness. And there is no doubt that he is doomed to continuous burning with sad and fearful cries and lamentations, but in vain. - [Badke translation/paraphrase]