Pictures taken by Montanez show the seeming reptile surrounded by driftwood at the edge of the water.
"I just happened to catch [it] out of corner of my eye," Montanez told WFSB-TV. "I thought it was maybe drift wood or something."
"I lived in Florida for a while so I knew what it was when I saw it," Montanez said. "I just wasn't expecting to see it here in Connecticut."
The Connecticut Department of Energy and Environmental Protection was alerted to the photos snapped at the scene by Montanez and sent investigators to the site, where they made an unexpected discovery.
"State Environmental Conservation (EnCon) Police responded to a report of a dead alligator in the Connecticut River, north of Hartford. As a result of the investigation it was determined that it was not a live alligator that died, it was a stuffed alligator," the DEEP said in a statement.