The US "Department of Homeland Security" (quotes intentional, and meant
to imply a certain distaste for their modus operandi) would *love* it
if the yachting community suddenly abandoned their Hatteras' for
mini-subs.

My guess is that they'd shoot first and ask questions later, and very
quickly proclaim that "any small craft that does not float (above) the
water shall henceforth and forever be illegal within 200 miles of any
US territory or possession!"

Wouldn't want to spook the natives when one of these poped-up next to a
ferry boat full of tourists on a pleasant afternoon on the San
Francisco Bay...

MW