What???? The only thing a boat in the Potomac could do is blow a bridge, or set off a dirty bomb. Not much of an immediate threat to human life in the immediate area.
A dirty bomb from a boat would be dumb. It would make more sense to do it from a plane.
I would argue that a dirty bomb could make quite a mess.
all flights from reagan natl fly their approaches down the potomac 1 psycho on a boat+stinger=disaster
A shoulder-launched antiaircraft missile fired from the deck of a boat on the Potomac could pick off airliners coming into Reagan Airport like clay pigeons on a skeet range.
A mortar battery mounted on such a boat could lob shells into the White House, Capitol, Marine Barracks, or any of a number of other targets.
And a boat could carry things a great deal worse than these...