 It appears it would have been difficult to flood the amphitheatre , but , because few records survive on the operation of the Colosseum , it is impossible to say for certain where the naval battles took place . Suetonius writes that Titus ' brother and successor , Domitian , staged sea @-@ fights in the amphitheatre , but he had made alterations to the structure , which probably included adding the <unk> — a complex of underground passages that may have allowed the arena to be quickly flooded and emptied . While Suetonius only records that Titus ' recreations of naval battles took place , Dio gives some details : 
