My grandfather was in a US Navy salvage group in WWII. At the time, to verify an enemy vessel (especially subs) had been sunk, they would send down divers in the old fashioned "heavy gear" suits to identify the vessels.
They would also bring up proof, usually something that could be tied to the vessel, which could be a piece of military-grade equipment or even silverware engraved with the names of the ship or the enemy seal.
They would also bring up proof, usually something that could be tied to the vessel, which could be a piece of military-grade equipment or even silverware engraved with the names of the ship or the enemy seal.
This is what the suits looked like:
https://en.wikipedia.org/wiki/Standard_diving_dress