It happened during a routine maintenance check of a fire boat, officials said.
It's not yet known how the firefighter fell into the water. The name of the firefighter has not been released.
"Camden's prayers are with the family, because he wasn't just a public servant. He was a husband, a brother, a father that committed his adult life to serving, and protecting, and being there for our residents in the city," said Mayor Victor Carstarphen during an afternoon news conference.
News conference on death of Camden, New Jersey firefighter
Rescuers were called to Wiggins Waterfront Park in Camden, New Jersey, around 11 a.m. for a report of a person who fell into the river.
Video from Chopper 6 showed rescuers surrounding a Camden Fire Department boat in the marina.
Water rescue scene in Camden, N.J.
They were able to pull him from the river, and he was taken to a waiting ambulance.
"This is a very difficult time for all of us. I do not have enough words that I can even say that could tell you how this is hurting all of us," said Camden Fire Chief Jesse Flax.
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