Charles Ellicott Commentary Exodus 15:10

"Thou didst blow with thy wind, the sea covered them: They sank as lead in the mighty waters." — Exodus 15:10 (ASV)

You did blow with your wind. — A new fact, additional to the narrative in Exodus 14, but in complete harmony with it. As a strong east (southeast) wind had driven the waters of the Bitter Lakes to the north-westward, so (it would seem) their return was aided and hastened by a wind from the opposite direction, which caused the sea to cover the Egyptians.

They sank as lead. — Compare Exodus 15:5. To an eyewitness, it would seem, the sudden submersion and disappearance of each warrior, as the waters closed around him, was peculiarly impressive. Each seemed to be swallowed up at once, without a struggle. This would be a natural result of the heavy armour worn by the picked warriors.

In the mighty waters. — With these words the second stanza, or strophe, closes. Miriam and her maidens, it is probable, again interposed with the magnificent refrain, Sing to the Lord, for he has glorified himself gloriously; the horse and his rider has he thrown into the sea.