tevah? An ark? Is this a box or is it a boat? The drawings of the two would be different.
In the epic of Gilgamesh, it appears to be a boat, if we are to trust the translation.
Tear down the house and build a boat!Though the dimensions being equal in length an width gives the idea of a cube. (Apsu seems to be the heaven or rakia, opposite tehom or tiamat.)
Abandon wealth and seek living beings!
Spurn possessions and keep alive living beings!
Make all living beings go up into the boat.
The boat which you are to build,
its dimensions must measure equal to each other:
its length must correspond to its width.
Roof it over like the Apsu.
But there are other bases for assuming it is a box. I recall seeing that in cognates in other languages, is means chest or ark, not boat.
However, the word only occurs in two places in Tanach, namely here and when the infant Moshe is placed in the Nile. Regardless of how it is used in other languages, we might develop a sense of what in means specifically in Biblical Hebrew, which is a container used for going on the water. Words have different connotations in different languages. For example, "mansion" in English is a stately, fancy house, but in Middle English, it just means "dwelling."
Meanwhile, in Egyptian, the cognate means coffin. This is indeed appropriate. We might cast it as fulfilling the literal aspects of the decree, while yet escaping. Thus, Noach, and UtanPishtim, are part of the entire world upon whom death has been decreed. They enter a coffin for the duration of the flood. And they exists through the decree of the flood. Moshe, too. Death has been decreed by Pharaoh on all Hebrew male born, by throwing them into the Nile. He is cast into the Nile, though in this tevah, coffin. And this fulfills the literal word of the decree. Indeed, a midrash stresses this by discussing how Pharaoh was told by his astrologers that a Hebrew child would overthrow him, which was the cause for his decree. When Moshe was cast in the Nile, his astrologers told him that they saw that the redeemer had been cast into the Nile, at which point Pharaoh ended his decree.
Since I mentioned Robert Alter in the previous post, I might as well mention his take again. Rather than noting the Egyptian cognate teva as coffin, he in fact contrasts aron, meaning coffin, with teva, meaning ark. He does this on the last perek of Bereishit, about Yosef's aron: