Coming from the "chilly North" (well, Scotland), I looked at the tales of Selkies that are found in Scottish, Irish, Icelandic and Faroese mythology. Selkies are creatures that can transform themselves from seals to humans. They do so by shedding their skins to assume human form and become seals again when they put them back on. Many of the tales are romantic tragedies - in some tales the man or woman does not know their lover is a selkie and wakes to find them gone; sometimes the human will hide the selkie's skin, stopping them from returning to the sea.
It is said that a selkie can only make contact with one particular human for a short time before they must return to the sea. They cannot make contact with that person again for seven years, unless of course, their skin is hidden -
Male selkies in human form are extremely handsome and have great powers of seduction over human women (I may have met one once, but that's another story...) Female selkies make good human wives, but always yearn for the sea, and will return if they can.
Selkies are not always faithless lovers - despite the Shetland Islands tales of them luring hapless islanders into the sea at midsummer, never to be seen on dry land again - for there is a tale of one fisherman who married a selkie and, against her wishes, set sail late in the season. He became trapped in a terrible storm and could not get back to shore. His selkie wife assumed her seal form and saved him, for she loved him deeply - even though this meant that she could never thereafter return to her human form.