en_tn_condensed/psa/046/003.md

though its waters roar and rage

"though the waters of the sea roar and rage." The words "roar" and "rage" describe the violent movements of the sea during a strong storm.

mountains tremble with their swelling

The phrase "their swelling" refers to the waters of the sea as they rise and crash against the mountains. Alternate translation: "the swelling waters cause the mountains to tremble" (See: rc://en/ta/man/translate/figs-explicit)