If you have heard of King Cnut, what you probably heard was the story of Cnut and the Tides. The most common version of it goes like this.
“Canute, the greatest and most powerful monarch of his time, sovereign of Denmark and Norway, as well as of England, could not fail of meeting with adulation from his courtiers; a tribute which is literally paid even to the meanest and weakest princes. Some of his flatterers breaking out, one day, in admiration of his grandeur, exclaimed that every thing was possible for him: Upon which the monarch, it is said, ordered his chair to be set on the sea-shore, while the tide was rising, and as the waters approached, he commanded them to retire, and to obey the voice who was lord of the ocean. He feigned to sit some time in expectation of their submission; but when the sea still advanced towards him, and began to wash him with its billows, he turned to his courtiers, and remarked to them, that every creature in the universe was feeble and impotent, and that power resided with one Being alone, in whose hands were all the elements of nature; who could say to ocean, ‘Thus far shalt thou go, and no farther’; and who could level with his nod the most towering piles of human pride and ambition.”