Director Peter Jackson reveals how the seven-minute waterlogged action sequence in The Hobbit: The Desolation of Smaug was created with a combined 98 hours of footage.
See Also : Making Smaug, Filming The Hobbit, The Desolation of Smaug
[youtube]https://www.youtube.com/watch?v=b45QQMg581o&list=UUftwRNsjfRo08xYE31tkiyw[/youtube]