In that day, the LORD will punish with his sword – his fierce, great and powerful sword – Leviathan the gliding serpent, Leviathan the coiling serpent; he will slay the monster of the sea.
NIV
IN THAT day [the Lord will deliver Israel from her enemies and also from the rebel powers of evil and darkness] His sharp and unrelenting, great, and strong sword will visit and punish Leviathan the swiftly fleeing serpent, Leviathan the twisting and winding serpent; and He will slay the monster that is in the sea.
AMP
In that day the LORD with his sore and great and strong sword shall punish leviathan the piercing serpent, even leviathan that crooked serpent; and he shall slay the dragon that is in the sea.
KJV