To kill a Unicorn is to bring bad luck and the hatred of nature itself down upon the foolish. It is said that the mate of a unicorn that is murdered will turn horrible in it’s pain and anger, turning against nature to hunt and kill the murderer of it’s mate. It turns dark and soulless and seeks nothing but the death of it’s enemy.
For a creation of the Black Tide of Acqua,death never truly befalls it. As long as the most vital part of it survives,the foul thing will continue to exist. In a certain sense..
Pirates' many bejeweled rings and piercings actually had a practical purpose - when the pirate or sailor died, the rings could be taken off as payment for a proper burial, saving him from a watery grave. This could be tied into regional culture, or made into a quest (The Pirate's Lost Rings, etc.). Also gives treasure-seeking divers another thing to look for besides crusty old chests.