In the Genesis account of Noah's Ark, pitch covered the vessel to make it watertight.
Genesis 6:14 tells Noah to cover the ark with pitch inside and outside. The material forms part of the construction instructions, alongside the use of gopher wood and the creation of compartments. Pitch was a waterproofing substance used in the ancient Near East to seal wooden boats and containers.
The Hebrew wording connects the ark's coating with the idea of covering or sealing, although translations differ in how they render the exact term. This is why some versions use “pitch,” while others use a related description such as bitumen or waterproofing material. The answer is not wax or clay: those substances may appear in other ancient technologies, but Genesis specifically identifies pitch in its ark instructions.