Though the waters... — The original is very expressive in its conciseness:
“They roar, they foam, its waters.”
Comp. Homer’s equally concise description, including in three words the “rush,” the “swell,” and the “roar” of ocean (Iliad, xxiii. 230).
Swelling. — Or, pride. (Comp. Job 38:11.) The change in construction in this verse seems to confirm the suspicion that the refrain has dropped away.