exodus 13:18 But God led the people about, through the way of the wilderness of the Red sea: and the children of Israel went up harnessed out of the land of Egypt. - Free Bible Online

      18. God led the people about, through the way of the wilderness of the Red Sea, &c.--This wondrous expanse of water is a gulf of the Indian ocean. It was called in Hebrew "the weedy sea," from the forest of marine plants with which it abounds. But the name of the Red Sea is not so easily traced. Some think it was given from its contiguity to the countries of Edom ("red"); others derive it from its coral rocks; while a third class ascribe the origin of the name to an extremely red appearance of the water in some parts, caused by a numberless multitude of very small mollusca. This sea, at its northern extremity, separates into two smaller inlets--the eastern called anciently the Elanitic gulf, now the gulf of Akaba; and the western the Heroopolite gulf, now the gulf of Suez, which, there can be no doubt, extended much more to the north anciently than it does now. It was toward the latter the Israelites marched.
      went up harnessed--that is, girded, equipped for a long journey. (See Ps 105:37). The Margin renders it "five in a rank," meaning obviously five large divisions, under five presiding officers, according to the usages of all caravans; and a spectacle of such a mighty and motley multitude must have presented an imposing appearance, and its orderly progress could have been effected only by the superintending influence of God.

JFB.