One notch in the rail. No license required.
The original owner of my boat (called Buckshee at the time) sunk a pirate boat off of Venzuela back in the late 70's.
He peppered their hull
at the waterline with an old M2, put a few into their engine
and then left them there.
If you look real close you can still see the patches on the our hull
He had secret compartments all over the boat filled with various rifles and pistols.