The Hebrew word for the ark is teba, which occurs only twice in the Bible, here and in the Book of Exodus, where it is used for the basket in which the infant Moses is placed by his mother. (The word for the ark of the covenant is quite different in Hebrew). In both cases, therefore, teba has a connection with salvation from waters. The etymology of the term is unclear, but most scholars connect it with an Egyptian word meaning a chest, box or coffin. It is made of "gopher" wood, a word appears only here in the entire Bible, and is divided into qinnim, a word which always refers to birds' nests elsewhere, leading some scholars to amend this to qanim, reeds, the material used for the boat of Atrahasis, the Babylonian flood-hero. Noah is instructed to kapar (smear) the ark with koper (pitch): in Hebrew the first of these words is a verb formed from the second, and this is the only place in the Bible where "koper" means "pitch". God spells out to Noah the dimensions of the ark, 300 cubits by 50 by 30, approximately 137 by 23 by 14 meters (440 feet long, 73 feet wide, and 43 feet high), with three internal divisions (which are not actually called "decks", although presumably this is what is intended), a door in the side, and a sohar, which may be either a roof or a skylight.

The story of the flood is closely connected with the story of the creation, a cycle of creation, un-creation, and re-creation, in which the ark plays a pivotal role. The universe as conceived by the ancient Hebrews was made up of a flat disk-shaped habitable earth with the heavens above and Sheol, the underworld of the dead, below. These three were surrounded by a watery "ocean" of chaos, protected by the firmament, a transparent but solid dome resting on the mountains which ringed the earth. Noah's three-deck ark represents this three-level Hebrew cosmos in miniature: the heavens, the earth, and the waters beneath. In Genesis 1, God created the three-level world as a space in the midst of the waters for mankind; in Genesis 6-8 (the flood story) he fills that space with waters again, saving only Noah, his family and the animals with him in the ark.

The parallels – both similarities and differences – between Noah's ship and that of the Babylonian flood hero Atrahasis have often been noted. Noah's is a rectangle, while Atrahasis was instructed to build his in the form of a cube; Atrahasis has seven decks with nine compartments on each level, Noah has three decks, but is not given any instructions on the number of compartments. The word used for "pitch" is not the normal Hebrew word but is closely related to the word used in the Babylonian story