The victim has been identified as 23-year-old Robert Miller of Glen Mills.
The body was discovered 75 feet north of the Golden Point Marina in Tinicum Township just after 11:00 a.m.
The initial 911 call came in around 3:30 a.m. from Robert's girlfriend.
She told police he went off the dock at the Golden Point Marina and didn't resurface.
Chief Stephen Edmiston of the Tinicum Township Police Department says at that time of morning the river can be very dangerous.
Miller's body will be taken to the medical examiner to determine the cause of death, which officials believe to be accidental drowning.
Miller had taken part in an end-of-season celebration at the boat club, but at this point, officials are reluctant to speculate on whether alcohol may have played a role.
A crew from Coast Guard Station Philadelphia and local police, fire and dive team members were brought in for the search efforts.