Albert Barnes Commentary Psalms 78:53

"And he led them safely, so that they feared not; But the sea overwhelmed their enemies." — Psalms 78:53 (ASV)

And he led them on safely, so that they feared not - In hope; in confidence; so that they had no occasion for alarm. He showed himself able and willing to defend them.

But the sea overwhelmed their enemies - Margin, as in Hebrew, covered. See Exodus 14:27-28; Exodus 15:10.