I have heard that this is a traditional mer-folk song that tells the tale of the dark side of mer-folk life. The author is unknown.

“Where Shells Are Silver and Bright”

The day shines clear; a knight has gone

Where shells are silver and bright.

Fish were leaping all around,

And sparkling was the light.

When there he paused, sounds

Came so sweet

Over every rock and tree.

A spell rose up and him it doomed

The mermaid’s face to see.

From ‘neath a rock, soon, soon

She rose,

And stately on she swam.

Stopp’d in the waves, and called

And sang

And to him stretched her hand.

So sweetly, sweetly did she sing,

It made his good sense sleep.

Out shot his hand – alas! Alas!

She’s drawn him to the deep!

Above the waves his ghost is seen

To wander back and fro.

While tides call up the black sea waves

And keening winds do blow.

– unknown author