It was a bit 'rougher' in the winter to get wet. I think I remember the procedure was to install the drain plugs, move the vehicle down to the water with the front wheels submerged up to the axles, turn on the sump pumps set on 'high', then ease into the water slowly and be very mindful of waves and wakes from passing boats, go out 100 yards or so, circle around and come back ashore. If it did not sink, it passed and the military accepted it. If it did sink, the manufacturer had to fix it and try again. The company did NOT want them to sink at all, but could not get the military to accept a higher freeboard on the sides of the driving compartment (three inches would have cut the initial failure rate to less than five percent). Uncle's reasoning was that the cab top would have had to be made higher to keep the opening large enough for the operators to get in and out of the driving compartment. In civilian hands, raising the front half of the driving compartment sides with a 2 x 12, cut to fit, allows it to operate in waves up to six inches in height without swamping. YMMV..
THAT would be a job I could enjoy. You would need to bring spare clothes to change in to.
After the first sinking of the day - how much worse could it get?
Especially if one in four were going to sink you could eventually come to work prepared.
I can see me eventually making a minor (unauthorized) modification after the first few sinkings.
The addition a couple of high volume sump pumps thrown in the driver's compartment might allow you drive it back to the ramp - above the water