This is weird history!
In the 6th century, during the reign of Justinian and Theodora, a “sea monster” usually described as a whale invaded the waterways of Constantinople and frequently attacked ships, sometimes sinking them. People nicknamed the whale, if whale it was, “Porphyrios,” and he menaced Byzantine shipping for some 50 years. All attempts to kill or capture him failed; he finally died when he beached himself and was cut to pieces by waterfront residents.
Most often drawn as a sperm whale, we don’t know exactly what he was. Whales don’t often appear in Constantinople’s waters. History records the beast as being some 45 feet long and 15 wide. That’s pretty much all we know. Oversized orca, maybe? Orcas have molested a few yachts and fishing boats recently, in the Bay of Biscay. But it’s hard to imagine a social animal like an orca living in isolation for five decades.
We are told St. Columba, a near-contemporary, spoke a word of command to the Loch Ness Monster which rendered it incapable of attacking human beings. They could have used him in Constantinople. Porphyrios’ depredations on local shipping were a black eye for the emperor.
It doesn’t seem like any whale behavior we’re familiar with. Just another mystery of history…