A Merman's Tail

Castiel was a merman who was born with the tail of a Great White Shark. Treated as an abomination by his own kind, Castiel found solace in observing humans and following their ships. He was content with watching them from afar, until he saved Dean, a human prince, from being killed by a shark. Soon, watching Dean from afar was not enough, and he wished to leave his life under the sea for a chance at being part of Dean's world.