These are the sea spirits in the folklore of the Orkney and Shetland Islands (Scotland area), which are similar to the Roane if the Hebrides. They are the Fin Folk or Seal People who appear as beautiful doe-eyed humans but must assume the misshapen form and skin of the seal, keeping only the beauty of their eyes, in order to reach their underwater caverns. They were thought to have been Fallen Angels that were too good to be sent to Hell and fell to the earth on the coastline. Sometimes they have been persecuted by humans, and if the blood of the Selkie is shed then this will result in a fierce storm and the loss of human lives at sea. The Selkie males are flirtatious and will often marry human women, but they are unreliable, and the marriage does not usually last. Children of such a marriage are said to have webbed fingers and toes.
--- Spirtis, Faeries, Leprechauns, and Goblins --- Carol Rose