According to Genesis, Noah used pitch to seal the biblical Ark against water.
Genesis 6:14 instructs Noah to make the ark from gopher wood and to cover it with pitch inside and out. Pitch is a waterproofing substance, historically made from tar-like or resinous materials, and was used to seal wooden boats and containers.
Translations vary in the precise wording of the Hebrew term, sometimes using “bitumen,” “tar,” or “pitch.” These choices describe the same general function: coating the wooden structure to reduce leakage. The passage does not identify a modern chemical formula or a single confirmed source for the substance.
The instruction to coat both the interior and exterior emphasizes waterproofing throughout the vessel. It is distinct from the ark's construction wood, whose identity is also debated because “gopher wood” is not securely identified with a known modern species.