It was in this year that Olaf (with his Swedish king assisting) did his grand feat upon Knut in Lymfjord of Jutland, which was already spoken of.

The special circumstances of which were these: Knut's big armament arriving on the Jutish coasts too late in the season, and the coast country lying all plundered into temporary wreck by the two Norse kings, who shrank away on sight of Knut, there was nothing could be done upon them by Knut this year,--or, if anything, what?
Knut's ships ran into Lymfjord, the safe-sheltered frith, or intricate long straggle of friths and straits, which almost cuts Jutland in two in that region; and lay safe, idly rocking on the waters there, uncertain what to do farther.

At last he steered in his big ship and some others, deeper into the interior of Lymfjord, deeper and deeper onwards to the mouth of a big river called the Helge (_Helge-aa_, the Holy River, not discoverable in my poor maps, but certainly enough still existing and still flowing somewhere among those intricate straits and friths), towards the bottom of which Helge river lay, in some safe nook, the small combined Swedish and Norse fleet, under the charge of Onund, the Swedish king, while at the top or source, which is a biggish mountain lake, King Olaf had been doing considerable engineering works, well suited to such an occasion, and was now ready at a moment's notice.
Knut's fleet having idly taken station here, notice from the Swedish king was instantly sent; instantly Olaf's well-engineered flood-gates were thrown open; from the swollen lake a huge deluge of water was let loose; Olaf himself with all his people hastening down to join his Swedish friend, and get on board in time; Helge river all the while alongside of him, with ever-increasing roar, and wider-spreading deluge, hastening down the steeps in the night-watches.

So that, along with Olaf or some way ahead of him, came immeasurable roaring waste of waters upon Knut's negligent fleet; shattered, broke, and stranded many of his ships, and was within a trifle of destroying the Golden Dragon herself, with Knut on board.

Olaf and Onund, we need not say, were promptly there in person, doing their very best; the railings of the Golden Dragon, however, were too high for their little ships; and Jarl Ulf, husband of Knut's sister, at the top of his speed, courageously intervening, spoiled their stratagem, and saved Knut from this very dangerous pass.
Knut did nothing more this winter.