I can think of a number of navigable channels less than 100 yards wide. Consider the Oakland/Alameda Estuary. A Navy ship at Todd's floating drydock could shut it down. Then there's the Napa River near Mare Island.
The Navy should be in charge of patrolling around their vessels. With container ships arriving and unloading totally uninspected, with those containers having full access to the North American continent, I think we have higher priorities for the Coast Guard than to harass American boaters (no, I don't have a boat), and I CERTAINLY don't think walking on the Constitution is necessary to protect American Naval vessels.
This is just about as dumb as the Federal Deputies inspecting old ladies at airports. Somebody should tell Mineta to unplug his butt and open his eyes. Better yet, he should be fired.