It happened around 2:30 Friday afternoon on the river between a naval base and Bellmawr, New Jersey.
Authorities say 23-year-old Casey Shubert was on his jet ski when he tried to ride a wave created by a tugboat.
As he tried to maneuver, the wave knocked him off the jet ski and left him unconscious.
Shubert was wearing a lifejacket and a tugboat crew member was able to tow him to safety.
The victim was taken to Hahnemann Hospital in critical condition.
An investigation into the accident continues.
