There really is no such thing as truly waterproof gear...unless it is a submarine.
Five years on the newer nuke boats confirmed for me that water does, in fact, get inside submarines, and get this... we bring it onboard intentionally.
Aside from Navy dive suits, with which I have no personal experience, even the rain gear used on submarines for stores loads, weapons loads, or maneuvering watch or topside watch or whatever... USN-issued rain gear is no more waterproof than, and usually less than, commercially available offerings.
Due to lowest bidder for the contracts?
Or due to the nature of water, always going to find a way?
You decide.
How deep do the nukes go? In the 70s it was Classified, not so today, but crush depth was rated at 2000, max operating depth was 1200. We were allowed to tell civilians 600.
Some guys would freak out hearing the hull groan and pop when we went deep, but it also did that coming back up. Intense pressure does things to steel things filled with air.