Permanently stop active water flow with Rust-Oleum Zinsser WATERTITE Hydraulic Cement for Concrete & Masonry. This fast-setting formula adheres to wet surfaces and expands as it dries, sealing deep cracks and holes with a watertight finish in just 5 minutes. Ideal for patching or anchoring, it’s available in 2.5 lb cartons and 10 lb pails. For best results, mix only what you can use within 3–5 minutes.