The man whose body was found Tuesday night in the upside-down PT Cruiser in Lycoming Creek was Aaron C. Moore, 22, of Williamsport, state police said.
Police said the 2001 Chrysler was reported stolen by the owner, a female acquaintance of Moore's, sometime Saturday.
Police did not identify the owner or say from where it was stolen.
Investigators told WNEP that Moore did not have a license and that the owner may have considered it stolen when Moore, who had borrowed the car, failed to return it.
The car was discovered in 6 to 8 feet of water under a Lycoming Creek Road bridge just south of the lower end of Heshbon Road by a couple walking across the bridge shortly after 7 p.m., police said.
It is believed that the crash occurred sometime Saturday because Friday night was the last time Moore was seen alive, Lycoming County Coroner Charles E. Kiessling said he was told.
Trooper Erik Barlett, the lead investigator of the crash, said Moore was traveling south on Lycoming Creek Road when it went off the roadway and struck a curb.
"The car continued traveling south, striking the end of a gurardrail that sent it airborne over an embankment and into the creek," Barlett said.
Kiessling pronounced Moore dead at the scene. He said investigators believe the driver, who was not wearing a seat belt, was knocked unconscious before the vehicle landed in the creek. He ruled Moore died from drowning.