In Genesis, Noah was told to use pitch to waterproof the Ark.
Genesis 6:14 says the vessel was to be covered with pitch inside and outside. Pitch is a thick, waterproofing substance traditionally associated with tar, bitumen, or related materials used to seal wood and other surfaces.
The instruction is practical within the story: a wooden vessel exposed to prolonged water would need its seams and surfaces sealed. The verse pairs this treatment with the instruction to build the Ark from gopher wood.
The Hebrew word translated as “pitch” is related to the idea of covering or coating. Translation traditions vary in the precise English wording, but the central image is the same: the Ark receives a waterproof coating on both sides.