A Scottish version of the mermaid, selkies were said to be creatures that can take the form of seals or humans, depending on whether they are in water or on land.
Once their seal-skins were discarded, selkies became extremely attractive to humans and it was not uncommon forrelationships to form, with the selkie making the decision to stay on land.
No matter how strong the selkie's ties with her mortal family, however, she would always pine to return to the sea, and so to avoid this possibility men would steal the seal-skins and hide them.Without their skins, the selkies were trapped on land.
A Shetland legend tells of a selkie woman who had been married to her mortal husband for many years and had several children by him (as everybody knows, any children produced by a selkie-human union can be distinguished by having webbed hands and feet).
One day, one of her young sons inadvertently discovered the seal-skin which had been secreted away in his father's hiding place and, wondering what it was, took it straight to his mother. Delighted, she seized the skin from him, put it on and slipped into the water, leaving her family, home and distraught husband behind forever.
Still, never mind. Plenty more fish in the sea, eh?