(One of my personal faves)
"Orkney(an island close to England) has many stories concerning a magical race of creatures known locally as the "selkie-folk" (meaning seal people). They are a rather gentle race of shape shifters with the ability to transform from seals into beautiful, lithe humans.
However often they transformed, the folklore tells us that once in human form the selkie-folk would dance merrily on the moonlit seashore or bask on outlying rocks or skerries.
A common element in all selkie-folk tales and perhaps the most important was that when the selkies assumed their human form, they shed their seal skins. Within the magical skins lay the power to change back to seals and therefore these had to be guarded at all costs. If one of the selkie-folk lost a skin, they were doomed to remain in human form until their magical skin was found again.
If disturbed during one of their midnight shore dances, the selkie-folk were known to quickly snatch up their skins and rush back to the safety of the sea.
The male members among the selkie-folk were thought to have had many encounters with human females, married and unmarried. A selkie man in human form was a handsome creature with almost magical seductive powers over mortal women. These selkie-men had no qualms in shedding their skins, stashing them carefully, and heading inland, seeking illicit intercourse with an "unsatisfied woman".
Should a mortal woman wish to make contact with a selkie-man, there was a specific rite that she had to follow - the woman had to shed seven tears into the sea at high tide.
Selkie females were no less alluring to the eyes of the earth-born men. A common theme in the selkie folklore are the tales of the cunning young Orcadian men who acquire either by trickery or theft, a selkie-girl's seal skin thereby preventing her from returning to her home in the sea. These individuals usually force the beautiful seal-maiden to marry them, very often siring children. The tales usually end sadly however, with the selkie wife's children finding and returning the sealskin so that she might return to the sea, more often than not taking her children with her. "
11.
http://www.pagerealm.com/windseeker/selkie.html