Mermaids
Very little is known about the people who live beneath the oceans except perhaps the rare sightings of beautiful people who are half-fish and half-person.  Yet it's generally believed that the Sea Elves know more about Merfolk than they are telling.
The Mermaid's Three Wisdoms
[Exerpted from The Mermaid's Three Wisdoms by Jane Yolen]
1. Have patience, like the sea.
2. Move with the rythm of life around you.
3. Know that all things touch all others, as all life touches the sea.
There have been many stories of Mermaids from fishermen, mostly saying the Mermaids enchanted human lovers with their beauty and songs. They were said to have caused many ship wrecks and storms. They were also said to be seen frequently combing their long hair and admiring themselves in mirrors.