an ancient Roman spectacle representing a sea-fight. It was sometimes exhibited in a circus or amphitheatre filled with water for the occasion; but more generally naval theatres, surrounded with seats and porticoes, and named after the spectacle itself naumachia, were constructed. The most celebrated of these were that of Julius Caesar in the Campus Martius, that of Augustus near the Tiber, and that of Domitian surrounded with an erection of stone. Claudius preferred to exhibit his naval shows on the Lake Fucinum. The naumachiarii, as the combatants were called, were usually captives or condemned malefactors. They were drawn up in two great opposing squadrons, distinguished by the names of any two maritime nations, and were doomed to fight until the one party had exterminated the other, unless the emperor, or the private person who had given the entertainment, put a stop to the engagement. The naumachia, like other Roman games, were often celebrated with the most extravagant pomp and magnificence. Artificial mermaids and sea-monsters were sometimes seen swimming among the ships; and the sight of two large fleets grappling with each other in deadly combat, to amuse a crowd of idle spectators, was no uncommon occurrence.