So at the end of the game, the people are on the boat, "Oh yay, we're free". NOT! The boat breaks down, and they're stranded. What do you think happens to them?
My theory is that, since you hear this weird low growl, the person you rescued, who had been bitten, chooses that unfortunate moment to become a zombie. Your character, who rescued said partner, is too shocked to do anything, gets bitten, becomes a zombie. If the Kelly or Hank person is in the boat, they get overwhelmed by the two zombies and get bitten. So the two or three zombies float around in a broken boat forever, or until it sinks. But that's just my theory.
