I service vintage Rolex oyster watches, vintage “dive” watches, and other pieces that originally carried a water resistance certification. But I do not provide certification, nor do I recommend swimming, bathing, or showering with vintage watches. It is important to understand that water resistance is not a permanent condition. Over a short period (under 2 years) gaskets will dry and harden compromising the original water resistance. If a watch is constantly exposed to chlorinated water, saltwater, or water with a high mineral content deposits will start building up as well as the resulting corrosion. This will permanently damage the case in joint areas that are critical to seal the watch.
Corrosion on a Rolex crystal/case joint 
The beginning of corrosion 
Severe Water Damage to Rolex 1570
Rolex’s Oyster Case water resistance
Rolex’s system of water protection is well engineered featuring the classic oyster case back, bezel friction fit crystal, and screw down crown. The gaskets are readily available can be replaced, and (depending on the condition of the case) can be sealed for reasonable water resistance. The cases were typically factory certified at 10 bar (100 meters). These vintage cases will usually pass a 3 bar (30 meter) test. That translates to protection from rain and splashing….but I do not recommend submersion or bathing while wearing vintage Rolex watches.
Other water resistant watches
Depending on the watch’s vintage, I can replace crystals, seals on both the case-back, crown seals, and pusher tubes on chronographs. However as mentioned, I cannot provide certification. Furthermore, I do not offer any guarantee of water resistance for vintage watches. My main objective for these pieces is returning them to working condition with reasonable water resistance. Use them for daily wear and enjoy them, but be cautious around moisture. Visit Why Waterproof / Water Resistance Rating Isn’t What It Seems for some interesting information. Please contact me with any questions.