The brother of Jared comes to the Lord with questions that arise from the construction of the barges. One of these comments is that “in them there is no light; whither shall we steer?” There are multiple implications of this question. The first is that the expected mode of steering a vessel required being able to see. This was, of course, the method used throughout most of history, and required not only the ability to see land (helpful only when land was close enough to be seen) but also to see the stars. Any transoceanic voyage would require the human pilots to steer by the stars. The brother of Jared comes to the Lord because the tight cover on the vessels (made according to the Lord’s requirements) make it so that they cannot see the stars. How will they steer?
The second implication of this statement is that while the Jaredites had built barges for the first voyage over the waters (presumably the Mediterranean), they did not have the waterlight “lids” on the vessels. The Jaredites would have been able to see the stars, and therefore this issue became relevant only upon this modification for the longer voyage across the Atlantic.
The second problem that comes from the watertight/airtight construction of the barges is that the air supply would be limited, and therefore dangerous. Both of these are new issues that arise from the apparently new instruction to lid the barges.