Yes, our stick on tiles are waterproof... With one caveat. You can use stick on tiles in bathrooms, but they shouldn't be used to tile showers. It's a bit too damp and the adhesive won't last as long as you'd like. There are products called "wet wall panels" which are suited to showers and won't allow moisture in (Google it! We don't sell them).
Do not hesitate to install stick on tiles above the sink in your kitchen or bath in your bathroom though, because that's exactly what they're designed for.
If you are considering using stick on tiles in a wet area, it is also important to ensure that the surface you are applying them to is clean, dry and free from any moisture or water. Failure to do so can result in the tiles not adhering properly and coming loose over time.
As long as you install them properly in an area that's not a shower, your peel and stick tiles will be waterproof for a very long time.