Here's something to think about. If this truck were used on land there would be a contact patch at the inner wheels, and due to deflection the outer wheels won't be carrying much of the weight of the vehicle. But in water all the wheels will be submerged roughly similarly, and will all contribute similar amounts of buoyancy. The total force will be the same to carry the total weight of the truck, but it will be moved much farther away from the center of the vehicle.

So from the perspective of the wheel bearings, bushings and control arms, is it actually harder on them to float in water than to sit on dry land?