The Ceasg or Maighdean na Tuinne ('maiden of the wave') is a Scottish mermaid of the Highlands.
The ceasg is half-human, and half salmon, the human half resembling that of a young woman like an ordinary mermaid.
These ceasgs were known to carry on love affairs with human males often marrying them. The off springs of these unions often produced great sailors and sea captains. These mermaids are repudiated to lure and seduce sailors to them in which the sailors never returned home.
If a ceasg was able to be captured and overcome she had the ability to grant three wishes. This was a difficult task to achieve because this was done by the destruction of her soul, which was kept safely somewhere else such as in an object or a land feature.