Legs Or Tails - Billdip Pirate AU

This is a fanfiction based on GravityFalls AU (Alternate Universe)
This is also based around the ship 'Billdip'. So if you have no interest in this ship I suggest you leave.

[Also the name is a pun intended, meaning 'heads or tails' but changed slightly]

Dipper is a young siren and wants to go adventuring, but his Uncle and society won't allow it.
Dipper discovers a younger siren being caught in a net and rescues the younger on but gets caught himself, he is then captured By Bill Cipher who is planning to sell him to the Gleeful's. But then he realises what is more valuable than money. His companion he had captured. But the sirens come to retrieve Dipper but Bill does something that makes it impossible for Dipper to leave him.