Filmmakers were shooting the 42-year-old "Of Men and Mavericks" star paddling out with competitive surfers Greg Long, Zach Wormhoudt and Peter Mel on Sunday afternoon, the San Mateo County Times reported.
The four were steering clear of a set of waves in the 15-foot range when a much larger set broke in front of them, said Wormhoudt, of Santa Cruz.
Butler was held underwater for two waves and washed through some rocks while tethered to his surfboard, Wormhoudt said. A safety patrolman on a Jet Ski swooped in and picked up the actor.
Butler was shaken up but not seriously injured, Wormhoudt said. He was taken by ambulance to Stanford Medical Center for examination and was later released.
Wormhoudt said Butler had not surfed much before the movie but had made an effort to improve his surfing and water skills for the film.
The group had talked about what to do if they got mowed down by big waves, and Butler wasn't trying to show off, Wormhoudt added
"Everything he was doing was within reason," he said. "We took like four to five pretty big waves on the head. Basically there's nothing you can do.
"It was intense for myself, and I've been through a lot out there."
Butler's publicist Rupert Fowler didn't immediately respond to an email message sent Tuesday. Coastside Fire District Battalion Chief Ari Delay would say only that a surfer sucked under by waves was on the beach when paramedics arrived. He wouldn't name the surfer.
"Of Men and Mavericks" is about Santa Cruz surfer Jay Moriarty, who conquered Mavericks as a teen but died in a free-diving accident in 2001 when he was 23.
Maverick's cold water and giant waves have made it a Mt. Everest-like conquest for some surfers. And it has impacted many lives, whether it be the death of legendary big wave waterman or serious injury to less experienced surfers seeking to make a name for themselves.
Last January, a surfer nearly drowned at Mavericks after being pummeled and washed through rocks by a big wave. That surfer, 30-year-old Jacob Trette of San Clemente, was rescued by an Australian firefighter who was on a personal watercraft taking photographs of the surfers when a large "freak set" caught a pack of them too close to shore.
Even the world's best surfers have been humbled by Mavericks, which has claimed its share of broken boards and bloodied surfers.
In 1994, Mark Foo, a seasoned big-wave surfer from Hawaii, died while surfing Mavericks. Ten-time surfing world champion Kelly Slater has also talked about how dangerous the wave is after getting held down after a wipeout there in 2000.