It happened in the Darby Creek near Creek and Station roads around 5:00 p.m. in Drexel Hill.
Officials say 25-year-old Christopher Scott of Clifton Heights dove 35 feet from a platform on a tree overlooking the creek.
Soctt landed in six feet of water and did not resurface.
Scott was pulled from the water a short time later.
An autopsy will determine whether he died from the fall or drowned.