The most important thing was a serious discussion about egress.
Excellent point and well executed.
Part of my maritime survival training was helicopter egress practice. Now helicopters have a strong tendency to flip upside down in a ditching. Which means you absolutely, positively will lose your bearings and have no clue whatsoever what is up, down, left or right, and where the emergency exit is. Furthermore, the cabin will be filled with bubbles, debris, oil and whatnot, so don't expect to see anything.
The trick is to ignore all this. Your seat will be bolted to the floor, and you will be strapped in your seat, so the emergency exit is still where it was before, in reference to your body and seat.
What you need to do is first clear the path to the emergency exit (which is normally your window, in an off-shore helicopter, so you open or eject the window), THEN you grab hold of the emergency exit (window sill or something) with one hand, THEN you unfasten your seat belt with the other. You then pull yourself towards the emergency exit and egress the aircraft.
I guess the same thing would apply to a C172. I expect that airframe to fill with water rapidly (especially once the doors are opened) so you need to be prepared for an underwater egress. That means that you will effectively be floating, more or less horizontally, in the cabin, once you released your seatbelt. And that means that the position of the front seats would not matter one bit, as you will simply float over the tops of the seats through the exit.