One of the most impressive scenes from the new Gladiator II film is the sight of the Colosseum being flooded with water ahead of a naval battle in front of a dazzled crowd – a spectacular form of entertainment to which audiences in Rome really were treated, albeit only on occasion. Known as a naumachia (plural naumachiae – literally ‘naval combat’), these maritime conflicts were staged not just in the Colosseum, but in certain other amphitheatres, natural lakes, and even specially-created pools during a brief period.

Blood & water

The naumachiae were in many ways an early Imperial phenomenon, first seen under Julius Caesar, and continued through the later first century BC and first century AD; after this they largely disappear from the written record, although it is unclear whether they were no longer held, or just no longer documented. At the height of their popularity, naumachiae even featured in Roman art, including several frescoes from the Temple of Isis in Pompeii.

All the known examples were organised in Italy, mostly in Rome and funded by the emperor, but naumachiae were almost certainly also staged in the provinces, albeit probably on a much smaller scale; the amphitheatre at Mérida (Spain) has a basin suitable for filling with water below the arena floor.

The earlier examples took place in specially-constructed large artificial pools, although over time the use of other venues was explored, including natural lakes and amphitheatres – and eventually, the Colosseum itself, albeit for a very brief period. The size of the venues used suggests that specially constructed scaled-down ships were likely used in the majority of naumachiae, particularly those held in amphitheatres, as there simply wasn’t room for full-sized vessels.

Size was less of a problem for those held in artificial pools or natural lakes, but they still probably followed the same practice, as it was noted by sources when one naumachia under Domitian used large ships (Suetonius, Domitan 4.2).

Many individual battles were themed around a particular historic event, often from the Greek world, with the combatants split into two groups portraying the respective combatants – Athenians and Persians ‘recreating’ the Battle of Salamis (480 BC) seems to have been particularly popular. There are no recorded instances of a Roman naval battle being recreated as a naumachia, which may have been an intentional choice, in case the side representing a victorious Rome should somehow lose in the recreation.

Although naumachiae were ‘mock’ naval battles, in practice they were deadly for the participants. The battles were brutal even by Roman standards, and usually featured condemned criminals and prisoners-of-war rather than trained gladiators; in most cases, there were no survivors.

The naumachiae were public entertainments, but in many ways they are better seen as mass executions, choreographed into an impressive spectacle. In one battle staged by Claudius, the skill of the fighters persuaded the emperor to let some of them live, but only once many had been killed.

However, when discussing a naumachia organised by Domitian, Cassius Dio notes that ‘practically all the combatants’ died (67.8.2) as if it was an unusual thing rather than the norm (many spectators also died due to a violent storm erupting during the fight, with no spectators allowed to leave).

Known naumachia

The first documented instance was staged in Rome by Julius Caesar in 46 BC, part of a programme of events in the city celebrating his victories in the Gallic Wars which also included traditional gladiatorial fights, beast hunts, chariot races, and athletic contests. There was no dedicated venue for naumachia in the city, so a large pool was dug out in a bend of the river Tiber within the Campus Martius (Cassius Dio, Roman History 43.23):

Finally he produced a naval battle, not on the sea nor on a lake, but on land; for he hollowed out a certain tract on the Campus Martius and after flooding it introduced ships into it. In all the contests the captives and those condemned to death took part.

Full-size ships were used in the battle, with up to four banks of oars, with the vessels taken from the allied fleets of Tyre and Egypt. However, it was prisoners rather than trained gladiators who took part in Caesar’s naumachia – captives taken during the wars in Gaul, and those condemned to death for crimes. The shows were so popular that spectators flooded into Rome from elsewhere in Italy, filling the city up so much that visitors could not find formal accommodation and had to pitch tents in the street – with some people crushed to death in the crowds.

Caesar’s successor Augustus also held a naumachia, in his case to celebrate the dedication of a temple to Mars Ultor in 2 BC – again, also alongside gladiatorial fights, beast hunts, and athletic competitions (Velleius Paterculus 2.100; Suetonius Augustus 43; Cassius Dio 55.10.7-8). It was staged in an enormous specially-constructed artificial lake created near Tibur island, surrounded by gardens. The venue was so large that it took its water supply directly from the Aqua Alsietina aqueduct (which carried water not suitable for drinking).

Thirty ships and around 3000 fighting men took part in the battle, which took the form of ‘recreating’ a well-known naval engagement from Greek history, the Battle of Salamis; the combatants, almost certainly also either prisoners-of-war or condemned criminals, took the roles of the ‘Athenians’ and ‘Persians’. The naumachia was such a spectacle that Augustus even included it on the Res Gestae, a monumental biography dedicated in numerous places around the empire (Res Gestae IV.23):

I gave the people the spectacle of a naval battle beyond the Tiber, at the place where now stands the grove of the Caesars, the ground having been excavated for •a length of eighteen hundred and a breadth of twelve hundred feet.​In this spectacle thirty beaked ships, triremes or biremes, and a large number of smaller vessels met in conflict. In these fleets there fought about three thousand men exclusive of the rowers.​

The emperor Claudius went one better than Augustus and staged a naumachia on a natural body of water in AD 52 – not in Rome, but in northern Italy on the Fucian Lake (Tacitus Annals 12.56; Suetonius, Claudius 21). It took part over a three-mile stretch of lake, with large banks of wooden seats built around it for viewers and a mechanism installed which could raise a platform in the middle of the lake during the performance. Rafts were situated around the combat zone to stop any of the ships escaping the battle, manned by soldiers of the Praetorian Guard who used their position to fire projectiles down on the engagement.

The scale of the battle was extraordinary. A large number of ships took part in the battle – up to 50 on each side – as did an astonishing 19,000 fighters, according to Tacitus. Once again, the combatants were condemned prisoners forced to fight – in this case, leading to an unusual situation which threatened to ruin the battle completely.

In the reign of Nero the first amphitheatre-based naumachia took place, in a wooden amphitheatre constructed on the Campus Martius in Rome (Suetonius, Nero 12; Cassius Dio 61.9). The amphitheatre was rapidly filled with seawater, within which were ‘sea monsters’ and fish, and a battle staged between combatants representing the Athenians and Persians at Salamis. As soon as the naumachia was over, the amphitheatre was drained and immediately used to host a large-scale gladiatorial combat; on another occasion, he appears to have done the same again, but then reflooded the arena floor and used it to hold an epic banquet.

The use of naumachiae to entertain the Roman public lasted longer than the Julio-Claudian dynasty did. While there is no record of Vespasian hosting one as emperor, his son Titus organised several (Suetonius, Titus 7; Cassius Dio 66.25) – one of which took place in the Colosseum, the arena floor flooded with water and (scaled-down) ships brought in to battle each other.

Again, the theme of the battle drew on Greek history, in this case the Corcyreans and Corinthians. Titus also organised a naumachia in the pool created by Augustus for his own over eighty years earlier, where 3000 combatants staged a naval engagement quickly followed by an infantry battle, fought between Athens and Syracuse –reconstructing an event from the Peloponnesian War.

Domitian also arranged a naumachia in the Colosseum (Suetonius, Domitian 5) around AD 85, although few details about the event are known. However, this was probably the last to be held in the Colosseum itself, as works in the sub-levels of the amphitheatre (hypogeum) to create a network of passages and cells used in gladiatorial fights and beast-hunts made it impractical to flood the arena for future maritime battles.

Domitian therefore created a new venue for such entertainments, a pool surrounded by wooden seating on the banks of the Tibur, where naumachiae were apparently held relatively regularly, seemingly with ships almost as large as those used by the real Roman fleet, seemingly a notable feature of these particular spectacles (Cassius Dio 67.8).

In the reign of Trajan, a new stadium for hosting naumachiae was built in Rome, on the Vatican hill on the other side of the Tibur from previous venues. Excavation showed that while it did have a substantial seating area, the surface area of the structure was only about 1/6 of the size of Augustus’ venue.

After the Flavian period, naumachiae appear to have gone into severe decline, and none matching the scale of the known examples survives anywhere in the historical record. There were good reasons to abandon them – they were expensive, and likely very logistically tricky to stage – but they may also have just become so normalised that Roman writers no longer chose to document them as historic events.

How were they staged?

Putting together a naumachia was a challenging enterprise – especially in the case of those held in venues which are described as flooded for a naval battle and then quickly drained ahead of a more conventional gladiatorial fight. The poet Martial at least suggests how impressive the flooding and draining of the Colosseum could be, with spectators unused to the sight seemingly unable to grasp the rapid change of the arena floor from ground to water and back again (Martial On the Spectacles 24):

“If you are here from distant land, a late spectator for whom this was the first day of the sacred show, let not the naval warfare deceive you with its ships, and the water like to a sea: here but lately was land. You don’t believe it? Watch while the waters weary Mars. But a short while hence you will be saying: “Here but lately was sea.”

Unfortunately, none of the Roman writers included any description of the engineering methods or any mechanisms, and only limited archaeological evidence has been found. The amphitheatres at Verona (Italy) and Mérida (Spain) have the only surviving examples of naumachiae engineering. Each has a basin below the arena floor, served with a conduit from a nearby aqueduct which would allow for relatively rapid flooding, while another allowed the arena to be drained.

The Colosseum likely had a similar basin in its earliest phases, before Domitian heavily renovated the substructure, and runoffs which may have been used to drain the water have been found within the amphitheatre (they may instead have just been used to channel away rainwater). It may have been easiest in many cases for an amphitheatre to have a sunken basin covered by a removable arena floor, allowing for rapid transition between the two forms of fight.

Conclusion

The Colosseum was flooded on occasion to stage epic sea-battles, fought by captured prisoners and criminals condemned to death. However, it was not the only place where naumachiae were staged, and other venues were used in Rome itself, Italy, and the wider empire – and in fact, the Colosseum was probably only used for these battles during the reigns of Titus and Domitian, before renovation of the arena’s substructure made such battles impractical to stage.

Nevertheless, the evidence demonstrates that the Colosseum was flooded to stage naval battles for public entertainment, as were other amphitheatres around the empire, and for this reason the claim is rated true.