Sussex Police said officers were called to New Road, Hellingly just after 11.10am on Saturday (May 14).
They were responding to a report of a body in the water, police said.
In a statement just after 4.30pm, a spokesman added: "The man unfortunately was pronounced dead the scene.
"New Road is currently closed while emergency services remain at the scene.
"The death is not being treated as suspicious and the coroner’s office has been informed."
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