Corryvreckan is the second (or third, depending upon the source) largest whirlpool in the world. It forms in the Gulf (or Strait ) of Corryvreckan, a narrow strait located between the islands of Jura and Scarba, off the western Scottish coast. During a flood tide, the natural topography of the area, in conjunction with the strong water current, creates whirlpools, standing waves and other effects on the sea's surface.
James Mason was originally cast as Torquil, but declined when told he would have to "live rough" in the islands. Ironically, Roger Livesey never went to the islands because he was in a West End show at the time. A double was used for long shots and all close ups are shot in the studio. Mason has always contended that it was Michael Powell's reluctance to pay the expenses of Mason's wife on the location shoot.
In 1947 Emeric Pressburger met the head of the script department at Paramount who told Emeric that they used 'I Know Where I'm Going!' (1945) as an example of the perfect screenplay which was shown to any writers stuck for inspiration or who needed a lesson in screen writing.
Although other names are authentic, there is no such island as Kiloran. It is, however, a village on the island of Colonsay, which is never mentioned, except in the credits. The map with 'Kiloran' written across it is in fact a map of Colonsay.