Wiped out

If every Egyptian soldier was wiped out when the Red Sea folded in on them, who other than the Israelites was left to tell all the other city states that were later fearful of the Jews because of what God did to the Egyptians. Was it Moses father in lawJethro who visited him in Ex. 18? It is also interesting that all 600,000 plu Israelites crossed the Red Sea at night. I always thought it was during the day.