In regard to Noah's Ark God commanded that it be built according to his dimensions and using something called gopher wood. The Ark was also to be coated with pitch in order to make it leak-proof and sea worthy (Genesis 6:14). Gopher wood's only mention in the entire Bible is in regard to Noah's Ark. This wood could have been the cypress tree used extensively by the Phoenicians. Another possibility is cedar wood. The 'pitch' used was likely bitumen, as there were extensive deposits of it in the Euphrates valley north of Babylon.
The above picture is a 1/32 scale model. This view shows the interior and the three decks God commanded Noah to make. The inside and outside was coated with pitch. A window was set 18 inches (one cubit) from the top (Genesis 6:16). Notice the Ark's size in the above picture in comparison to the larger animals such as the hippopotamus! Also note the caging system used for the animals.
How BIG was the inside? God stated its dimensions were to be 300 by 50 by 30 cubits. If we assume a cubit is roughly 18 inches (45.7 centimeters), the ark was 450 feet (137.2 meters) long, 75 feet (22.9 meters) wide and 45 feet (13.7 meters) high. The volume of the ship would be 1,518,000 cubic feet. The actual floor space would be more than 101,000 square feet (9,383 square meters)!
Only air breathing, land based animals were taken on Noah's Ark (see Genesis 6:17,19-20, 7:22). Animals like whales, dolphins, alligators, fish, turtles, lobsters, etc. etc. didn't need saving from the flood since they already could live in water! That leaves roughly 40,000 or less animals, with the average size being that of a sheep, needing to be put on the ship. When fully loaded only 30% of the space was taken up by animals!