The pair used a 5-pound magnet to cast their line into the C-102 canal in Princeton and after about 5 minutes, they pulled up a Barrett .50-caliber sniper rifle.
A few minutes later, they pulled up an identical rifle, Smith said.
Smith said both guns were missing their barrels and had their serial numbers filed off.
The rifles were turned over to the Miami-Dade County Police Department.
Detective Christopher Thomas said police will perform tests to try to determine whether the guns were used in any known crimes.
A Michigan man previously discovered an unusual piece of weaponry while magnet fishing in April 2021. Ryan McCollum said he and his son were magnet fishing in Grand Rapids' Grand River when they reeled in a a 2-foot-long metal object that turned out to be a World War II-era artillery shell.