According to Genesis, Noah’s Ark was sealed with pitch. Genesis 6:14 instructs Noah to cover the vessel inside and outside with pitch, creating a waterproof coating.
Pitch is a thick, sticky substance made from materials such as wood tar or petroleum residues. In ancient boatbuilding, related bituminous substances were used to reduce leakage and protect wooden structures from water. The biblical instruction therefore has a practical maritime function within the story.
Translations vary in how they render the underlying Hebrew term, sometimes using “bitumen” or another waterproofing substance. “Pitch” remains the traditional English answer and matches the wording in many familiar Bible translations.
The pitch was not the ark’s building material. Genesis separately names gopher wood for construction and pitch for sealing. Confusing those two details produces an answer that combines two different instructions from the same verse.