Destiny: The Vampire Mermaid.

In Crimson Currents Destiny is captured by female pirates who have a private enterprise selling women to an unknown buyer. They decide to use Destiny's underwater talents to make a greater profit. However the vampire mermaid will not be controlled. Next in Death in the Dark Destiny takes the pirate Mary Reid with her on a quest to destroy Dracula. In Dracula's castle she soon finds the king of vampires not so easily defeated.