Nephi has previously used the story of the destruction of Pharaoh’s army in the Red Sea, in 1 Nephi 4:2. On that occasion he was encouraging his brothers to return to Laban in spite of his ability to raise a small military force against them. At the time it was a story of God’s power to protect them against a powerful foe, and perhaps to foreshadow the death of Laban.
In this case, it is simply a reminder that God can overcome all obstacles. That is the reason that Nephi quickly follows the story of the Pharaoh’s armies with the story of the miraculous provision of food and water. Thus, the children of Israel were under Jehovah’s protection in their journey through the desert.
The obvious lesson for Laman and Lemuel was that they had already been miraculously preserved through the desert, and they could therefore expect that Jehovah would also overcome the small difficulty of building a ship.