Won't need to after they hold your head underwater for 10 mins if you have survived the ditching!
On that assumption RVDT, once you have delivered the package to its destination, they will do you in anyway.
At least if you ditch, chances are you will know what is going on and know how to operate the door jettison. You should get out ok!
Once in the water and the hijackers survive, perhaps they will realise that they need to try and survive. A few miles out to see I would have thought survival would rather kick in as opposed to trying to kill the person who in their mind has just saved them from a helicopter crash!
Don't forget, If they try and hold your head underwater for 10 minutes, they are also in the water. They do not have the same stability as when that sort of thing is done in films with baths or washbasins. The person doing the holding has to have a stable base or they go down aswell!
This isn't the movies you know.
