Officials say two joggers discovered the body around 5 p.m. in a wooded area near Merion and Narberth Avenues, about 50 yards from a residential area.
It took firefighters several hours to pull the man's body from the marsh. Investigators say the body had been in the marsh for several days and showed signs of decomposition. Police also say the man had distinctive tattoos that may help to identify him.
"There were some tattoos on him which we're running right now," said Lieutenant Frank Falco of the Camden County Prosecutor's Office. "Hopefully the tattoos will identify who he was."
At this point, detectives are labeling the man's death as "suspicious."
Throughout the night, police went door to door, informing Haddonfield residents of the gruesome discovery.
"It's troubling," said Craig Wolff. "We're going to have to be really diligent in looking around and seeing who's around us. You see it on TV but you don't see it in your backyard. It's not something you want to see."
Police suspect the man's death was an isolated incident. As a precaution however, police plan on sending out extra patrols through the neighborhood over the next few days.
"In Haddonfield these things don't happen very often," said Neal Rochford of Haddonfield Public Safety. "We just want to take the abundance of caution to make sure our residents feel safe."
An autopsy to determine the exact cause of death is scheduled for Tuesday morning.