Police tell the Syracuse Post-Standard the body of 53-year-old Kirk R Jones was found in the Niagara River by the US Coast Guard on 2 June.
Detective Sgt Brian Nisbet of the New York State Park Police says it's the same man who became the first person to survive an unprotected plunge over the falls in October 2003.
Nisbet says investigators believe Jones attempted to go over the falls inside a 10-foot (3m) ball on 19 April. The empty ball was recovered by the Maid of the Mist tour boat.
Three others have survived unprotected plunges over the falls since Jones did it.