Bam Margera's PAINFUL Kayak Disaster -- Caught on Tape

Bam Margera's guts busted through his abdominal lining when he plummeted over a 100 ft cliff in a kayak ... and now TMZ has obtained footage of the stunt that sent Bam to the E.R.

We broke the story ... the "Jackass" star needed emergency surgery to fix a nasty hernia he sustained during the kayak stunt at an Oregon waterfall last week with pro kayaker Steve Fisher.

In the footage, Fisher warns Margera to "tense everything" before they go off the cliff -- but when the duo smash into the water, the force of the impact was so intense, Bam was ejected from the vessel ... and he suffered damage to his abdominal wall.

Moments after the stunt, Bam was seen smiling and laughing ... but he soon realized something was wrong and went to a hospital ... where doctors performed emergency surgery to treat the hernia.

When we caught up with Bam after the incident, the daredevil told us he might need more surgery in the fall.