Flex Glue Incredibly Strong, Waterproof Adhesive. This legendary super strong, waterproof adhesive with powerful instant grab and hold is now engineered with Easy Squeeze technology for smooth, easy dispensing. Specifically formulated to work on all types of surfaces and can be applied on dry or wet surfaces, even underwater. Solvent-free, paintable, sandable, and won't run or drip so it can be applied overhead. It's UV, chemical, and mildew resistant too, making it ideal for both indoor and outdoor use.