Naumachia was a large-scale performance of past maritime battles with the purpose to stage actual historical combats. It was a special occasion sponsored by the emperor which accumulated expensive costs and difficult tasks, such as filling and draining the stadium with water. Naumachia was staged in two formats, one where the site was an actual and exciting lake, or the other in an artificial lake built over an amphitheater. It was performed by slaves and criminals who played to battle against each with as much as 19000 men. The performs played roles of soldiers and warriors in opposite squadrons, and wore costumes that fit historical combats' time and place.
This entertainment activity was performed with smaller ships due to the stadium size restrictions. It also took place in water-filled basins with temporary constructions for playing nautical battles in the Campus Martius.
I participated in one of the Naumachia battles with a thousand sailors and approximately the double number of rowers. The battle was re-act of the famous battle between the Egyptian and Tyrian fleets. It took place in the Campus Martius which was a low-lying area in a bend of the river Tiber. This Naumachia happened after my return from a triumph battle, that was the civil war near Thapsus in 46 BCE. However, the life and death were real when the Roman crowds camped on streets, and died to when watched others being killed mimicking the sea battle.
This sport was the favorite for Roman people, and even for other regions who came to watch it and risk being killed in the crowds.