When Bilbo and the dwarves escaped Thranduil's kingdom, they did so in empty wine barrels, rushing down the forest river, fighting wood elves and the rapids simultaneously. Their escape was a breeze compared to what director Peter Jackson and the actors went through to make the scene, as this Wired video reveals.
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Garland - Last Top Comment on Splinter
I hated this part of the movie. There were a few areas where the CGI was so obvious and poorly done that I lost all immersion in the movie. It was worse than most of the CGI work in those crappy SyFy original movies.