Is jewellery waterproof?

Yes, it is.  Gold, silver and platinum can all be worn in water. It will not damage the metal if they are true to their caratage. The vast majority of stones can be worn in water as well. however, do pay attention to opal and pearls. They can yellow over time but if you happen to get thrown in to a pool or caught in the rain, it will not damage them. but as with anything, always rinse off your jewellery and allow to dry. I would suggest doing so with the items off your skin, especially with any hollowed-out rings. Moisture often traps in the cavity against the skin, and this creates a rash. 

Watch silver jewellery should you be in a salt water as it can make it tarnish if it is very salty. 

After all is said and done, jewellery at the final stage of manufacturing all lands up in an ultrasonic for the removal of polish residue.