Sea-monster

To thee Poseidon, Lord of the sea, did Amyntichus give these his last gifts, when he ceased from his toil on the deep—his nets edged with lead that plunge into the sea, his oar still drunk with the brine, his spear for killing sea-monsters, strong lance of the waters, his weel ever betrayed by floats, his anchor, firm hand of his boat, and the flint, dear to sailors, that has the art of guarding the seed of fire.

Source: wiktionary

With naked swords we slashed through the waves / ready with warblades for wandering whales / dark sea-monsters.

Source: wiktionary

There are many references in antiquity to this story of an earlier Trojan War, in which Hercules, after killing a sea-monster and rescuing the princess Hesione, requested the princess as a bride in reward for his work.

Source: wiktionary