"The physics of a whirlpool this size overwhelmed the team at ILM [Industrial Light and Magic, the effects company]. The path we were heading down was not achieving the desired results so it all had to be reworked. The initial rendered backgrounds were used as out of focus plates for close-ups which bought us time by getting 100 or so shots in the pipeline and allowed us to completely rethink and re-render the maelstrom for all of the wide shots. This is the exact opposite of how you would normally go about producing this sequence. John Knoll and the team at ILM ultimately pulled it off, but it was a real nail-biter."