In the biblical Book of Genesis, Noah is instructed to use pitch to make the ark watertight.
Genesis 6:14 describes the ark as being made from gopher wood and says that Noah should cover it inside and outside with pitch. Pitch is a waterproofing substance, traditionally understood as bitumen or a similar resinous material. The instruction reflects the practical need to seal a large wooden vessel against water.
The Hebrew word translated as “pitch” is related to a verb meaning to cover or coat. Translations vary slightly, but the basic idea remains the same: the ark receives a protective coating on both sides. The passage does not identify gopher wood with a securely known modern tree species, so “pitch” is more certain than any proposed identification of the timber.
This detail is separate from later artistic depictions of the ark, which often show ordinary wooden planks without a visible waterproof coating.