In Genesis, pitch sealed Noah's Ark against water.
Genesis 6:14 tells Noah to cover the Ark inside and outside with pitch. The instruction follows the command to build the vessel from gopher wood and is the story's explicit waterproofing detail. Pitch is a thick, water-resistant substance traditionally associated with tar or bitumen, although the precise ancient material is not settled by the verse.
The word is sometimes mistaken for the Ark's building material, but Genesis distinguishes the two: gopher wood is the structure, while pitch is the coating. The Hebrew wording also creates a wordplay between the verb for covering with pitch and a term connected with atonement in some translations.