Utnapishtim used bitumen to make his boat watertight in the Epic of Gilgamesh.
In Tablet XI, the flood hero follows instructions to build a huge boat and seal it with bitumen. Bitumen is a naturally occurring petroleum-based material that was widely used in the ancient Near East as a waterproofing substance. Its use fits the practical needs of a wooden or reed-built vessel in Mesopotamian environments.
This detail resembles the use of waterproofing in other ancient flood traditions, but the wording and measurements differ between texts. Genesis says Noah coated the Ark with pitch, while the Gilgamesh account names bitumen in the boat-building process. These are related ideas, not evidence that the two narratives use identical construction instructions.