Horrific footage shows a 10-year-old boy being thrown from a water slide onto concrete just 90 minutes after the water park opened.
In the video, the boy shoots out of the Emerald Plunge slide at The Wave water park in Dublin, California, before being hurled over the edge of the slide on his back.
He then skids along the concrete for metres as other park patrons watch in horror, news.com.au reported.
According to the East Bay Times, the boy was "shaken up" and grazed his shoulder but was otherwise unharmed.
The park closed the Emerald Plunge ride after the accident, which was captured by a photographer attending its grand opening.
Emerald Plunge drops its riders at an 80 degree angle before it flattens out at the bottom. A description on the park's website says "a severe drop induces thrills in this open air ride.
"Prepare for a rush as you drop three storeys at an 80 degree slope."
According to the Mirror, spokeswoman Shari Jackman said the park was "re-evaluating that slide".
Emergency services were not called and the boy was assisted by a lifeguard.
The Mirror reported Dublin assistant city manager Linda Smith witnessed the boy's accidentand said: "He got up immediately and as any boy would be, he was stunned."