When the truck gets to the bottom of the hill, it does not land upright, it keeps rolling into the water, and the cab topper also comes flying off the truck and into the water (very obvious to see if you pause and scroll forward slowly) yet in the next shot, the truck is not only out of the water, it is perched at angle that is impossible due to the way it was rolling down the hill, and the cab topper is back in place.
Al's Cat 2 MRAP is retrofitted with a customized gun setup on the roof. Even the handle is after-market. How would Martha know how to operate it, let alone with proficiency, after driving the truck around for one day? It's unlikely that Al wrote up an instruction manual.