Oceans Requitement

Oceans Requitement
or
Wave After Wave

This is a tale as it has not been told for a long time.
A throwback to the original legends of bloodthirsty mermaids woven together with a modern take on witches of both land and water, this story is about young Madeline and how she is adopted by the sea; given a new name; and is offered the opportunity to wreak vengeance.
A hint?

She takes it.