Ridley Scott’s “Gladiator II” is full of a memorable action scenes, from a bloody showdown featuring CGI baboons to Paul Mescal outsmarting a charging rhino in the Roman Colosseum. But one sequence that is sure to leave audiences with the most questions is a rather insane set piece in which the Colosseum is filled with

Sharks? Maybe not. But sea battles, semi-aquatic creatures and plenty of other eye-popping spectacles were part of the real-life games at the ancient Roman Colosseum.

To mark the opening of the Colosseum in 80 C.E., the Roman emperor Titus staged a staggering spectacle, flooding the arena with water and bringing in “horses and bulls and some other domesticated animals that had been taught to behave in the liquid element just as on land,