A lot of people have beef with the ocean. There's even a word for the people who have a phobia of it: thalassophobia. Not many people have been so intimidated by the deep blue sea, though, that they've declared war on it.
Enter Caligula. The Roman emperor between the years of AD 37 to 41 wasn't known for his smarts. In fact, after an uneventful first six months of his rule, he became known as a tyrant who ruled with an extravagant brutality.
Eventually, his sadistic acts got him assassinated.
Before his death, though, one of the battles he allegedly wanted to win was against Neptune, the Roman god of the sea.
Most Romans worshipped him, but Caligula apparently thought the god was a hurdle along the way to capturing even more power.
The story originates from an account from Gaius Suetonius Tranquillus, the historian who recorded much of what we know about the early Roman empire.
He claimed that on one of the emperor's trips to Brittenburg, a Celtic and Roman ruin off the coast of the Netherlands, Caligula decided Neptune needed to be defeated.
He lined up his soldiers and artillery along the beach and ordered them to take to the sea in battle.
When the ensuing water fight was "over," Caligula claimed victory and had his soldiers collect shells as souvenirs of their win. It was reportedly one of the many instances in which the emperor appeared to be losing his mind, and one of the episodes that convinced his bodyguards to band together to carry out his assassination.
Historians aren't sure if the story is true, or if it's a tall tale that's been passed down or exaggerated through several centuries.