How many watches can be exposed to salt water?
I would say any brand with a significance among the military and National Security communities (especially specialist diving units) - Rolex, CWC, Tudor, Omega, but also G-Shock, Garmin and Suunto to name a few...
Tool watches are integral parts of military history.
The $20 casio F91 is ingredibly durable and almost as tough as any G-shock. Easily replaceable if lost or damaged - it may even prove cost effective to just buy a fresh watch once the battery expires.