Charles Ellicott Commentary Exodus 14:30

"Thus Jehovah saved Israel that day out of the hand of the Egyptians; and Israel saw the Egyptians dead upon the sea-shore." — Exodus 14:30 (ASV)

Israel saw the Egyptians dead upon the sea shore. — For someone who saw this sight, it would likely make a great impression; for later generations, it was nothing, since it had no further consequences. That it is recorded indicates the pen of an eyewitness.