Corrected entry: When Ben was tied up underwater, he shot the gun to untie himself. That is not possible because the gun would of been inoperable.
Corrected entry: When Bigg Bunny goes to take off from the water, he pushes the throttles fully in. A few shots later, he pushes the throttles fully in again.
Correction: The plane had to slow down to turn around before finally taking off. It is when he is finally taking off when he pushes the throttle in the second time.
Corrected entry: The cave where the treasure is stored is known to be "a cave for two days" and a deathtrap the rest of the year. If this is a readily known fact, doesn't that imply that someone has been in the cave already (and would have already found the treasure)? Otherwise how would they have known that there was a cave and that it was occasionally dry?
Corrected entry: The entire movie takes place around Key West and, later, the Bahamas. However, in several scenes, mountains or large hills are visible in the background. Such topography does not exist in the Florida Keys and the Bahamas.
Correction: The credits list the shooting locations as the Bahamas and Queensland, Australia. Kate Hudson mentions in the bonus interview that she loved filming in Australia. This would account for the differences in terrain features. Similarly, the character "Moe Fitch" was a representation of a Key West icon: Mel Fisher who discovered the ship "Nuestra Senora de Atocha".
Correction: It's very possible actually. As the gun was only recently dropped it water, rust wouldn't be an issue, bullets are sealed so water can't get in, and most importantly Finnegan fired a shot from point blank range, so the water would have had less chance to impede the bullet's velocity.