Each item I create is 💧 waterproof. Please note that if the item should get wet, you would want to dry it gently with a soft cloth and it will be fine. I think the best advise would be to treat it the same as you would any nice piece of costume jewelry and it will last.
The simplest way to avoid tarnish and damage is to store your piece in a sealed 'Ziploc' style bag or in an air tight container. The air causes metal to oxidize thus giving a dull appearance. Using a good jewelry cloth to polish your item also works very well.