It is said in the films that "Bootstrap" Bill Turner was tossed in the water tied to a cannon, after the crew of the Black Pearl took the Aztec gold. It seems he was already undead, therefore the pirates had to find his son to get his blood and break the curse.
But in the second film, we learn that Bill Turner is part of Davy Jones' crew, which implies that he died in the sea and bargained with Jones to get something in exchange of serving him in the Dutchman.
So how much time was Bill Turner actually underwater?
And what was the bargain?