According to Genesis chapters 6-8, Noah, his wife, Noah's three sons (Shem, Ham, and Japheth), and their wives were on the ark. Therefore, there were eight people on the ark.

Noah is warned of the coming flood and told to construct the ark. God spells out to Noah the dimensions of the vessel: 300 cubits in length, 50 cubits in width and 30 cubits in height (450 × 75 × 45 ft or 137 × 22.9 × 13.7 m). It had three internal divisions (which are not actually called "decks", although presumably this is what is intended), a door in the side, and a tsohar, which may be either a roof or a skylight.

It is made of "gopher" wood, a word which does not appear elsewhere in the entire Bible, and is divided into qinnim, a word which always refers to birds' nests elsewhere, leading some scholars to emend this to qanim (reeds), the material used for the boat of Atrahasis, the Babylonian flood-hero. God instructs Noah to kapar (smear) the ark with koper (pitch): in Hebrew the first of these words is a verb formed from the second and, like "gopher", it is a word found nowhere else in the Bible.

Noah is instructed to take on board his wife, his three sons, and his sons' wives. He is also to take two of every living thing, and seven pairs of every clean creature and of every bird, together with sufficient food.

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