John Calvin Commentary Psalms 33:7

"He gathereth the waters of the sea together as a heap: He layeth up the deeps in store-houses." — Psalms 33:7 (ASV)

He gathered together the waters of the sea as into a heap. Here the Psalmist does not speak of all that might have been said about every part of the world, but under one aspect he includes all the rest. He celebrates, however, a striking and remarkable miracle which we see when looking at the surface of the earth: namely, that God gathers together the element of water, fluid and unstable as it is, into a solid heap, and holds it so as He wills.

Scientists acknowledge, and experience openly proclaims, that the waters occupy a higher place than the earth. How is it then that, as they are fluid and naturally disposed to flow, they do not spread out and cover the earth, and how is it that the earth, which is lower in position, remains dry? In this we certainly perceive that God, who is always attentive to the well-being of the human race, has enclosed the waters within certain invisible barriers, and keeps them contained even to this day; and the prophet elegantly declares that they stand still at God's command, as if they were a heap of firm and solid matter. Nor is it without design that the Holy Spirit, in various passages, presents this proof of divine power, as in Jeremiah 5:22, and Job 38:8.

In the second part of the verse, he seems to repeat the same idea, but with amplification. God not only confines the immense mass of waters in the seas, but also hides them, by a mysterious and incomprehensible power, in the very depths of the earth. Anyone who compares the elements among themselves will consider it contrary to nature that the bottomless depths, or the immeasurable gulfs of waters, whose natural tendency is rather to overwhelm the earth, should lie hidden under it. That so many hollow channels and gulfs, accordingly, should not swallow up the earth every moment, provides another magnificent display of divine power; for although occasionally some cities and fields are engulfed, yet the earth itself is preserved in its place.