It IS water tight
Used this after my quad tendon repair. It kept my wound & dressing dry through several showers.  It was a bit difficult to don on a knee that couldn't bend, but bunching it up and stretching open the gaskets to get it over the foot took care of that. Once past the foot it will easily stretch over the knee region. Just make sure you create a dome effect for the top gasket. That ensures the water will run off rather than pool and wet your dressing when you remove it.
Rating: 4 stars