Christ alone can take away sin, animal sacrifices cannot (Hebrews 10:4). From the beginning of the world, God planned that Christ would become flesh. From the beginning, God knew that Noah and his family would be the lone survivors of the flood. He knew that the Messiah would be a descendant of Noah— that the Messiah would be the only way in which man could find favor. The saving of Noah from the flood was part of God's plan from the beginning. Thus God, in order that his purposes would be brought about, commanded Noah:
Make for yourself an ark of gopher wood; you shall make the ark with rooms, and shall cover it inside and out with pitch. (Genesis 6:14)Nobody knows exactly what gopher wood is (or at least, no one who is alive knows). Commentators suggest various types of wood that this passage could be referring to: cypress, pine, cedar, and more... The most that can be said with certainty is this: Noah made an ark. He made it out of some type of wood. And the wood that he used was named after a gopher (because, after all, gopher's like wood).
As described Genesis 6:14, the ark had rooms... it wasn't just a giant empty wooden tub. The gopher wood structure of the ark was covered with pitch. Concerning the pitch on the inside of the ark, John Gill, in his commentary on this verse, states that it served to "take off the ill smell that might arise". The pitch on the outside held the ark together, which prevented leaks, thus enabling it to float.
The type of wood and the pitch are just the first among many details which the book of Genesis gives about the ark. The next few verses provide much more information, especially regarding the dimensions of the ark.
How Big Was Noah's Ark? - Genesis 6:15-16
Noah Found Favor In The Eyes Of The LORD - Genesis 6:8
The Pre-Flood World Soon To Be Blotted Out - Genesis 6:7
State of the World (2948 BC): Noah's Birth - Genesis 5:28
Man in the Image of Man - Genesis 5:3