Excellent idea, on the egress training!!
I watched a single-engine on floats flip over... we were taxiing in and they were ahead of us, touching down on the water.. it was scary to see, but fortunately soon two heads popped up above the water, each next to a float.
I've talked to two other pilots who survived ditchings, and they each kept repeating the same thing: they could not believe how FAST the airplane sank, in each case. Again, good fortune prevailed, and they had just enough time to get rafts out, etc., and were rescued (each had passengers), but they were still shocked, years later, at that one thing.
I always figured empty places in fuel tanks and fuselages would (or at least, with luck, could) somehow contribute a little flotation, but they each said they had believed that once, too, and it was wrong.
Just their two cents' worth.......