I occasionally get asked about whether or not yacht owners and crews should have access to weapons to assist in dealing with "pirates"." I generally advise against anyone (homeowners or boat owners) who is not experienced with weapons or combat in close quarters acquiring anything other that a shotgun for home defense.
There is a very good article, written by Dave Kellerman, available at MaritimeSecurity.com:
Obtain formal training and education in the handling and employment of a firearm, to include a thorough understanding of "deadly force" issues. Those that think the mere possession of a firearm provides an increase in security are ignorant. Without proper education and training, the firearm is a liability, not an enhancement to security.More on Remington tactical shotguns here.
UPDATE: I'm not giving you legal advice, but it is a really, really good idea to know the laws pertaining to weapons and use of deadly force in the areas where you live, transit and visit.