The Viva La Bam star took a kayak over a 100ft cliff in Oregon, leaving him badly injured, E! reports.
Despite his injuries, he tweeted about the jump just moments later, saying: "Just did a 100ft tandem kayak jump with pro kayaker Steve Fisher in Oregon!"
Margera, who is now in stable condition, sent more messages to fans from his hospital bed, explaining that he had to undergo a hernia operation.
The 32-year-old is best known as a star of the Jackass TV show and movies.
He was involved in an Australian street fight and arrested for disorderly conduct in New Orleans earlier this year.