The ancient Mesopotamians had it right when they began using asphalt to waterproof temple baths and water tanks. The Phoenicians later found asphalt useful in caulking the seams of their merchant ships. And when they needed to seal their baths, reservoirs, and aqueducts, guess what substance the Romans relied on? Thousands of years later, asphalt has a proven track record documenting its ability to resist water penetration.