In the biblical story, Noah used pitch to waterproof the Ark.
Genesis 6:14 instructs Noah to cover the ark with pitch inside and outside. The coating would seal the wooden structure against water, at least within the practical imagery of the narrative.
Pitch is a thick, waterproofing substance historically associated with bitumen, tar, or resinous materials. Ancient boatbuilders used related substances to seal seams and protect wood, although the precise material intended by the Hebrew word is not certain.
This detail is distinct from gopher wood, the material named for the ark’s construction. Genesis gives both details in the same verse: gopher wood forms the vessel, while pitch coats it. Later retellings sometimes mention only a wooden boat and omit the waterproofing instruction.