(CNN) -- His hashtag said it all: not a good idea.
Steve-O, best known for his grimace-inducing stunts on the "Jackass" TV show and films, was in San Antonio this weekend and flipped out. Literally.
A photo shared on Facebook some 7,000 times (a related video got over 10,000 shares) shows the wild man in mid-leap. "I did a good deed today by proving it's not safe to jump off the bridge at the San Antonio River Walk," he wrote. "It's shallow — I hit the bottom when I landed this gainer flip. #notagoodidea"
Not safe because the water is only about 4 feet deep. It's also illegal.
City statutes forbid anyone jumping into or swimming in the San Antonio River. Doing so can mean a $500 fine.
San Antonio Police Sgt. Javier Salazar said authorities are looking into the incident "to determine the appropriate course of action."
It's not clear if the entertainer will have to open up his wallet. Maybe he should consider himself lucky by walking away from the river stunt.
"It's all fun and games until you shatter the bottom of your legs," wrote one fan on his Facebook page. Another chiming in: "Wouldn't you check how deep the water is first?"
Steve-O told the Houston Chronicle he "had no idea the water was only four feet deep when I jumped off this bridge." Later, he issued a statement blaming city officials for being "quite irresponsible in neglecting to post 'no diving' signs on the various bridges along the river."
"They've given no indication that people shouldn't jump, and done nothing to warn anyone about the serious dangers of that shallow water," Steve-O said. "Very irresponsible, indeed."
The actor/daredevil added that authorities should be thanking, not investigating, him for his jump.
"I think they should be thanking me for informing people, rather than wasting their citizens' time and money trying to vilify me," he said.
Although he has thrilled and disgusted audiences with low-brow antics, in recent years Steve-O has showed a more thoughtful side. Last year, he talked to HLN's Jane Velez Mitchell about his involvement in a documentary about farm animals and his recent decision to go vegan and get sober.
But it's not all high brow. Just three days before his San Antonio plunge, Steve-O posted an Instagram video of a throwback stunt with striking similarities.
"Back in 1996, I did a flip off a building into 4 feet of water while it was snowing, and landed on my face," he wrote "#yeahdude."
CNN's Greg Botelho contributed to this report.