What did the children of Israel cross when coming out of Egypt? The Red Sea or some lake or some section of the southern Mediterranean Sea? Nowadays, if you look at most maps in the back of your Bible, it seems that Israel didn’t come anywhere close to the Gulf of Suez in their Exodus journeys out of Egypt.
This helpful and convincing article by Overstreet allows the Bible to answer that question: R. Larry Overstreet, “Exegetical and Contextual Facets of Israel’s Red Sea Crossing” TMSJ 14 (2003): 63-86.
Acts 7:36 and Hebrews 11:29 are convincing enough, but, as Overstreet makes plain, other Old Testament references to Yam Suph make it close to impossible to take Yam Suph as some obscure lake between Suez and the Mediterranean Sea.
Also see Victor Hamilton’s commentary, where the question is made helpfully plain: “I fully agree that by itself sup means ‘reeds,’ but must it mean that in the combined expression yam-sup? Is there any body of water in the delta region of Egypt that was ever known or identified as yam-sup? If that can be answered positively, then that would certainly tilt the translation toward ‘Reed Sea.’ To the best of my knowledge, however, the answer is a resounding no.” Exodus: An Exegetical Commentary [Grand Rapids, Mich.: Baker Academic, 2011], 206-7.