The psalm begins with a condition said twice: if it had not been the Lord who was on our side, let Israel say. The repetition underlines that the people did not come through by their own strength.
Verses 3 to 5 describe what would have happened. When men rose up against them, they would have been swallowed alive in the heat of their anger. The waters would have overwhelmed them, a torrent would have swept over them, and raging waters would have covered them. The images of a monster swallowing its prey and of a flood express a threat they could not stop.
From verse 6 the tone is praise: blessed be the Lord, who did not give us as prey to their teeth. The people escaped like a bird from the snare of the fowlers; the snare was broken and they were free. The psalm ends with a confession: our help is in the name of the Lord, who made heaven and earth.