In Genesis, Noah's Ark was coated with pitch.
Genesis 6:14 instructs Noah to make the ark from gopher wood and to cover it with pitch inside and out. The coating was intended to make the wooden vessel watertight, sealing gaps and protecting the structure from the floodwater.
The Hebrew term translated as “pitch” is related to a word for covering or coating. English translations differ in their exact wording, but “pitch” is the traditional answer in many English versions. The passage does not identify a modern chemical formula or specify the tree species meant by “gopher wood.”
Readers sometimes answer “tar” because tar is also a waterproofing substance. That is understandable, but “pitch” is the canonical wording in the King James Version and many trivia references. Bitumen is a related natural material, not the wording normally expected for this question.