Re: D'oh
No, I think what has happened was this:
He lowered outdrive, started engine with the muffs, reves it up, but forgets to put truck in a parking, or apply parking brake. And, because it is Bayliner, prop produced enough thrust in the air to push this entire setup forward. But obviously nobody was in the truck to push the brake, and by the time he realised what is going on, was too late.

I can only imagine how fast would it go in the water.