According to Genesis, Noah used pitch to seal the ark against water.
Genesis 6:14 tells Noah to cover the ark inside and outside with pitch. The instruction describes waterproofing a wooden vessel, an essential practical detail in the construction account. English translations may use related terms such as bitumen or tar, because the ancient substance and the precise Hebrew vocabulary do not map perfectly onto one modern product.
Pitch is a general waterproofing material rather than a special timber. This detail is sometimes confused with gopher wood, which is the material named for the ark’s construction. Genesis mentions both: gopher wood forms the vessel, while pitch coats it. The text does not provide a recipe, quantity, or modern chemical identification for the pitch, so claims about an exact substance go beyond what the passage states.