The Caoineag (KHOO-nyak) is a Scottish spirit similar to the Irish banshee. Her name derives from the Gaelic caoin, meaning weep, and caoidh, meaning mourn. She is one of the Fuath, the malevolent spirits or fairies that inhabit Scotland’s waters.
When the tide is at the turning and the wind is fast asleep,
And not a wave is curling on the wide, blue deep,
Oh, the waters will be churning in the stream that never smiles,
Where the Blue Men are splashing round the charmèd isles.
from Wonder Tales From Scottish Myth And Legend by Donald Alexander McKenzie
The Blue Men of the Minch are a group of mythological humanoid creatures that inhabit the waters of the Minch, a strait in the north-west of Scotland that separates the mainland from the northern Outer Hebrides.