Still, there's no added margin of safety to be had from a higher pressure rating at swimming/snorkeling depths. The watch leaks or it doesn't; a thicker crystal and case won't help the soft seals hold one bit. I've been using a 50-m rated Rolex from the '70s in the sea regularly, just as it was designed to do, without any issues. I'd have no hesitation with using a modern Milgauss to its full rated depth, aside from being a wimp who wouldn't want to go that deep under water even if paid to do so.
Anyway, when Rolex states a depth rating, they mean it. They've built their reputation on keeping water out of the case; 100 m is more than enough for anyone but a commercial saturation diver. It would likely even suffice for that; they're known to hugely underrate their pressure resistance.