The victim's name had not been released pending notification of family members.
9-1-1 calls reporting "a body in the water" near Thunder Road came in about 2 p.m.
Lt. Peter Szpakowski, a Trenton police spokesman, told MidJersey.News that off-duty city firefighter Akyse Watkins dragged the man's body to the shore.
Watkins tried to revive the victim as other first responders from Mercer County arrived, according to media reports.
Police, firefighters and EMS crews were called on a report of "a body in the water" about 2 p.m.
Trenton police told NJ Advance Media that first responders initially were unsure if the victim had been in the water a few minutes or a few hours.
At this point, police consider the drowning to be accidental.
Trenton Det. Brian Jones is leading an investigation into the man's death.
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