Please, don’t stick that vintage watch away in a safe, put it on your wrist – enjoy it and show it off on IG for the rest of us to check out!
Some caveats:
– If your dive watch was originally intended to be waterproof and noted so, you can still use it as such – just swap out that nice leather strap, make sure to have your watch regularly serviced (perhaps more frequently than if you aren’t wearing in the water), and have it pressure tested (this is a “dry” test) by your watchmaker. Depending on how much you use the watch in the water, you may want to consider getting it pressure tested by your watchmaker regularly. We’ll comment that many collectors won’t take their vintage dive watches anywhere near water, and prefer swapping to a modern watch when hitting the water. We can’t say whether or not they have read this excellent and entertaining post on vintage watches and water Myth Busting…. again. If you do take it for a dive, rinse afterwards – salt may impact older watch material, and you don’t want any corrosion (similar for chlorine).
– Dust and humidity, including rain, are not friends of your vintage watch. If you are going to hang out at the pool or do some gardening, consider swapping off that vintage chronograph (more pushers = more entry points) for a modern watch. If your waterproof watches is fogging, moisture must have entered the watch (or moisture was in the watch when sealed), so you may want to have it checked by your watchmaker.
If you do live a humid environment, or are headed on vacation, it is important to understand what types of cases will protect your watch from moisture. The Rolex Oyster case (1926), Gallet Clamshell 4-screw case (1936, built upon rights to a “waterproof” design (Brevet N° 189190) from Schmitz Frères & Cie) and super compressor cases (1950s+ from E. Piquerez S.A., both here and here) cases, all of which offered a degree of protection. But don’t expect upon purchase that your vintage piece, regardless of source, is waterproof – it’s a good idea to make sure the watch and seals are in good condition and that it passes a pressure test.
Some collectors are comfortable traveling to humid locations, or simply in and out of areas with vastly different temperatures (think of existing a nice air conditioned building out into the Florida heat), and believe that leaving the crown open will allow the watch to “breathe” and pass the air in…and back out of the watch. I wouldn’t personally do that, preferring to make sure it’s been testing, and the crown is secured.