Within 20 miles of where the diver popped up in the Hudson River is the "Indian Point Nuclear Plant;" two conventional power plants; the Marcy South Power Line, which runs under the Hudson right where this guy was found and feeds electric juice to NYC and Long Island; the Catskill Aquaduct, which runs under the Hudson right where this guy was found and feeds water to NYC; West Point Military Academy; and three bridges, including the six lane "Hamilton Fish Jr. Bridge," which services I-84 across the Hudson between Beacon and Newburg.
Query: Suppose these divers planted underwater explosives timed to go off some time in the future. How long could the explosives remain under water before going bad?
they might be able to damage some of the inlet pipes, but they certainly cannot blow up the reactor with explosives planted in the water outside. in any case, they are probably inspecting the plants now because of this incident.