You trampled the sea with Your horses, churning the great waters.
This passage draws its language throughout from earlier revelations of God in Israel's history, especially Moses' song in Deuteronomy and the Psalms. Habakkuk is not merely recalling past wonders as comfort; he is predicting a future coming of the Lord to judge the nations, as the future tense at the head of the description makes clear.
AI summary
Commenting on Habakkuk 3:3-15
Some read, “Thou hast trodden thy horses in the sea;” but it is a solecism, that is quite evident. Others, “Thou hast trodden in the sea by thy horses.” But what need is there of seeking such strained explanations, since the verb דרך, darek, means to go or to march?
Thou didst walk through the sea with thine horses-- (Hab 3:8). No obstacle could prevent Thy progress when leading Thy people in safety to their inheritance, whether the Red Sea, Jordan, or the figurative waves of foes raging against Israel (Psa 65:7; Psa 77:19).