Stryd is splash-proof and even IP67 compliant. However, you cannot use Stryd when running through puddles, streams and rivers. The reason is that water can be forced into the device since the pressure can be more than what Stryd is designed to handle.
It is safe to clean Stryd with water and mild soap. Do not use anything abrasive or harsh chemicals to clean your Stryd.
If you are worried about the run history stored on your Stryd (for example when you are giving your existing Stryd to another runner), you can remove the history only by uploading the data from Stryd with the Stryd app on your phone (this can cause duplication of data in your account, contact us if that is a concern for you).