Wow. Isn't the first rule of gun safety keeo your muzzle pointed in a safe direction at all times? Another is a safety is a mechanical device and mechanical devices can fail. Thats where another rule comes to mind, never travel with a loaded gun. When hunting, never load your gun until you are in position to use it on your game. Not saying he deserved it but, he sure wasn't taking the right steps to avoid the accident.
He's damn lucky he wasn't walking back to the boat when this happened. But that is perhaps the gene pool's loss.