In the Eye of the Whirlpool

"It had been written in blue, in the middle of a strait that separates two Inner Hebridean islands—one small and little known called Scarba, and another, larger, called Jura. At the northern side of this strait, two-thirds of the way toward its Atlantic exit, the map said, with neither comment nor explanation, 'Whirlpool.' The body of water in which it was sited was known as the Gulf of Corryvreckan: whatever it was that lurked two-thirds of the way along it was therefore known as the Corryvreckan Whirlpool.
But hold on! Whirlpools, I thought, were mythical entities, not the kind of thing to put on a modern-day map."