Gerard Butler nearly drowned when a 20 foot wave broke on his head whilst filming a scene at Mavericks, California.
Jonny Weston was hired with no prior film or commercial acting work. He was discovered via an audition video he submitted via a casting website where anyone who's looking for modeling or acting work can sign up for, create a profile and audition for work.
Gerard Butler was briefly hospitalized when a surfing stunt went wrong. Part of his recovery involved a heavy course of painkillers. Butler would later check himself into the Betty Ford Clinic to wean himself off these painkillers.
Gerard Butler was a very inexperienced surfer before taking on his role in the film. Jonny Weston, on the other hand, had been surfing for about 10 years.