Note:  Do not rely on this information. It is very old.

Naumachia

Naumachia (Greek "sea-fight"), in ancient Rome, was a public spectacle, consisting of the representation of a naval battle, in which gladiators fought as they did in the amphitheatre. The first naumachia took place on a sheet of water in the Campus Martius, made for the purpose by Julius Caesar (46 B.C.).