Why not? There are places in Canada where tides regularly retreat 17 meters — vertically! Why could something like that not have happened at the sea at the time described in Sefer Shemot?
Because the Torah said it didn’t. What happened to the rest of the story? Moshe stuck out his arm with the staff and the sea split. The midrashim tell us it split into 12 parts, had freshwater springs, grew fruits and that the ground was dry. In addition all the water in the entire world split as well. We can hardly attribute this to the moon.