That it was not the Red Sea, but the Reed Sea. There was a translation error that was just transmitted down the millenia.
"...Location of the crossing
Crossing the Red Sea, from Dura Europos synagogue, 3rd centurySee also: Yam Suph, Red Sea, and Reed Sea.
The Israelites' first journey is from Ramesses to Succoth. Ramesses is generally identified with modern Qantir, the site of the 19th dynasty capital Per-Ramesses, and Succoth with Tel el-Maskhuta in Wadi Tumilat, the biblical Land of Goshen.[3] From Sukkoth the Israelites travel to Etham "on the edge of the desert," then turn back to Pi-hahiroth, located between Migdol and the sea and directly opposite Baal Zephon. None of these have been identified with certainty. One theory with a wide following is that they refer collectively to the region of Lake Timsah, a salt lake north of the Gulf of Suez, and the nearest large body of water after Wadi Tumilat.[4] Lake Timsah was connected to Pithom in Gesem at various times by a canal, and a late 1st millennium text refers to Migdol Baal Zephon as fort on the canal.[5]
The Hebrew term for the place of the crossing is "Yam Suph". Although this has traditionally been thought to refer to the salt water inlet located between Africa and the Arabian peninsula, known in English as the Red Sea, this is a mistranslation from the Greek Septuagint, and Hebrew suph never means "red" but rather "reeds."[6] (While it is not relevant to the identification of the body of water, suph also puns on the Hebrew suphah ("storm") and soph ("end"), referring to the events of the Exodus).[7]
General scholarly opinion is that the Exodus story combines a number of traditions, one of them at the "Reed Sea" (Lake Timsah, with the Egyptians defeated when the wheels of their chariots become clogged) and another at the far deeper Red Sea, allowing the more dramatic telling of events. [8]
The Hebrew term yam suf really means 'reed sea'.[9] Reeds tolerant of salt water flourish in the shallow string of lakes extending from Suez north to the Mediterranean Sea. Kenneth Kitchen and James Hoffmeier state that these reedy lakes and marshes along the isthmus of Suez are acceptable locations for yam suf.[10][11] The ancient yam suf is not confined to the modern Red Sea. Hoffmeier equates yam suf with the Egyptian term pa-tjufy (also written p3 twfy) from the Ramesside period, which refers to lakes in the eastern Nile delta.[12] He also describes references to p3 twfy in the context of the Island of Amun, thought to be modern Tell el-Balamun.[13] Tell el-Balamun was the most northerly city of Pharaonic Egypt, located at (31.2586 North, 31.5714 East), about 29 km southwest of Damietta.[14][15] ..."
http://en.wikipedia.org/wiki/Crossing_the_Red_Sea
The Reed Sea is a lot shallower, so normal tides can explain "the parting." NO tsunamis are required to explain it.
In case you still believe that Wikipedia is unreliable, here's another source that says the same thing:
http://www.ucg.org/science/bible-and-archaeology-red-sea-or-reed-sea/