I have been very conservative in my comments here about the 2nd amendment but I generally think the definition of arms should be broadly (liberally, if you will) defined. However, other points of the amendment give much more trouble.
While I doubt there were many cannon parked in people's carriage houses during the 1780s and 1790s, it is true there were armed merchantmen (commercial sailing ships) at the time. Here the sticking point is that the owners of those ships had to obtain letters to permit them to act as privateers or, private warships. That system was also in place in other countries at the time. Such licenses only authorized the holders to attack only ships of certain other countries that we happened to be at war with. The lack of such a license essentially made them pirates. Perhaps you have heard of pirates. That's where the expression "shores to Tripoli" came from, fighting them where they lived.
Private ship owners did not want to become privateers out of patriotism but rather because of the profit motive, which still exists, apparently.
More to the point, however, is the question of exactly why they just had to go and mention the militia, which, contrary to some folk's idea, was not the whole people. It was a legally defined body (which excluded well over half the population) and it was mostly compulsory. Chances are, were it the same today, people would kick at the idea of compulsory military service, even if it were only for local defense purposes.
If the second amendment were replaced with a rewritten amendment, how doyou think it should read?
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.