My guess is that ther sapphire may be thicker on the Submariner,, which theorically needs a bigger water resistance.
I don't think the case has a different construction.
As for the movements, they are basically the same, except that the Explo II has, of course, a GMT function.
But if you want to dive with your Explo II, no problem.
I guess you won't dive 300 meters deep, by the way.
Best,
Nicolas.
This message has been edited by amanico on 2012-07-25 07:45:06