Augustine of Hippo

And he continues how? "The waters have seen You, O God, and they have feared and the abysses have been troubled" [Psalm 77:16]. What are the waters? The peoples. What are these waters has been asked in the Apocalypse, [Revelation 17:15] the answer was, the peoples. There we find most clearly waters put by a figure for peoples. But above he had said, "You have made known in the peoples Your virtue." With reason therefore, "the waters have seen You, and they have feared." They have been changed because they have feared. …

Exposition on Psalm 77 ↗

Ambrose of Milan

This is not the only example of the obedience of water available to us, for elsewhere we find it written, "The waters saw you, O God; the waters saw you, and they were afraid." What is said here of the waters does not seem to be without a semblance of truth, since elsewhere the prophet also speaks in the same manner: "The sea saw and fled; Jordan was turned back." Who does not know how in actual fact the sea fled at the crossing of the Hebrews? …

The Six Days of Creation 3.1.2 ↗

Jerome

The waters saw you, O God, the waters saw you, and they feared. For the moment let us speak according to the letter; let us cling to the earth for the sake of the simpler folk. When the people passed through the Red Sea and through the Jordan, the waters understood their Creator, and the people did not understand. And the depths were troubled. "The sea saw, and fled: the Jordan was turned back." The great sound of the waters. "The clouds shook out the waters," it has in the Hebrew. The clouds gave forth their voice. …

Homily 10, on Psalm 76 ↗