The Orkney Finfolk

In Orkney folklore, Finfolk are sorcerous shapeshifters
 of the sea, the dark mysterious race who regularly make an amphibious 
journey from the depths of the Finfolk ocean home to the Orkney Islands. 
They wade, swim or sometimes row upon the Orkney shores in the spring 
and summer months, searching for human captives. The Finfolk kidnap 
unsuspecting fishermen, or frolicking youth, near the shore and 
force them into lifelong servitude as a spouse

 Rackwick fishermen, Orkney

The Finwife starts her life as a beautiful mermaid bent 
on acquiring a human husband. The Finman is described as being tall, 
dark and thin with a stern, gloomy face. He is said to have many magical 
powers, such as rowing between Norway and Orkney in seven 
oar-strokes, making his ship invisible and creating 
fleets of phantom boats

by Edmund Dulac
According to folklore, the under water dwelling of the Finfolk, 
known as Finfolkaheem (literally 'Finfolk's Home'), is regarded as the place 
of origin for the Finfolk, and their ancestral home. A fantastic under water 
palace with massive crystal halls, Finfolkaheem is surrounded, inside 
and out, by ornate gardens of multi-coloured seaweed. They 
love anything made of silver; coins and jewellery

The Orkney Islands on the Carta Marina, 1539
by Olaus Magnus (1490-1557)

A lobster fisherman in Kirkwall, Orkney

To capture the unsuspecting human bride or groom, the Orkney Finfolk 
cunningly disguise themselves and their fins as other sea animals, plants or 
even as floating clothes. The Finfolk kidnapping attempt begins by approaching 
the prospective mate cautiously, floating ever closer, until it is possible to leap up 
and grab the victim. The Finmen often use another tactic, appearing in human 
form disguised as fishermen in a row boat. The Finwife prefers a more 
natural form, and often appears as a beautiful mermaid 

Seaweed heart