Marcus,
I wear my Ploprof extensively as a beater. It gets knocked around quite a bit and the sapphire bezel is holding up very well. In fact, I don't think it is any less durable than the sapphire crystal over the crystal. But as you and your diver friends may worry its position on the outer edge may increase exposure to hard contact unnecessarily. That is something I can agree with but I am not worried about it. 

My example is dipped in salt water more than a few times. But it's not frequent enough to qualify as a measure of resistance. So far the only issue I had with the watch is its tendency to catch sand inside of the sliding clasp. Other than that I have no complaints. I do everything with this watch. I even shoot with it. Handgun, shotgun, everything, no problem.
I hope this helps.
Ruckdee