Fin or Finn Folk are a species specific to Orkney folklore that do not seem to have spread to their sister islands, the Shetlands and the Faireys. Fin folk may are may not be classed as Fair Folk, depending on the tale being told but, unlike Seal Folk, there is no pretence of them ever being human.
Fin Men and Fin Wives are attractive while they are young, and only rarely described as anything other than human looking. The Fin Wives are occasionally said to have fish tails but this may be a borrowing from the more widespread mermaid mythology (so far unconnected to the Otherworld). Young Fin Folk are often enchanted by the idea of a human spouse and will kidnap lone people on the shore.
Tradition holds that they have two homes: the undersea Finfolkaheem (literally Fin Folk’s Home) and the mysterious, unseen island Hildaland (Hidden Land). Despite the insistence that no-one returns from these, descriptions are paradisaical.
These tales were dismissed for many centuries by English and Scottish academics but modern interpretation is leaning towards a similar explanation to that of Seal Folk, although there is division over whether the Fin Folk are the spirit forms of a seaweed colony or an Otherworld subspecies of fish, as with the Merrow. It is generally accepted that Finfolkaheem would be a seaweed forest and Hildaland an Otherworld island.
The short-range Ranger reconnaissance programme for 2015 is intended to investigate this matter further but Unnatural Resources Orkneys will not be publishing the results until 2017.