Perhaps the Bible's description of the vessel being called an 'ark' (meaning chest or coffer) instead of a 'boat,' offers a clue as to its functional shape
The last poster is absolutely correct, the point is mute. However since this was the argument the WT used to say it was a box shape, it is worth analyzing. The word 'tevah' (an Egyptian loan word, ark) is only used two times in the Tanakh (OT). The second time it refers to a pitch coated floating (basket?) Moses was placed in when put in the Nile. Clearly the author was linking the two stories, stories of divine passage through water. (another time). I never saw the WT depict Moses in a box. That's all I'm saying.