They are waterproof Janet. I think because they stick together underneath the wood looking part.
From Home Depot:
Easy GripStrip installation Lays directly over your old floor; no floor prep or messy glue needed! Looks and feels like real wood feel the knots! Completely waterproof. Perfect in high moisture areas basements, kitchens, and bathrooms. Warm comfort and quiet under foot. Install an entire floor cleanly, easily in just a few hours. 25 year residential warranty.
Also - from Youtube: