In Somalia, pirate activity is regarded as normal free market activity and an accepted way of earning a living.
Due to the various hostage risks in Somalia, including charity aid workers, it is not practical to blow every pirate ship up because it could provoke revenge hostage taking & retribution. Pirates generally target commercial shipping, because that is simpler and more lucrative due to a company being involved rather than mere private individuals. This is one reason why they can and will intercept ships hundreds of miles from the shore re commercial gain.
Whilst government (may) have not paid ransom, commercial entities have therefore the "never pay" has been undermined.
The advice not to go anywhere near Somalia was ignored, probably due to the incorrect and rather naive belief "they will not intercept us in a simple old yacht" based on what they see rather than what a pirate sees. Perhaps such beliefs will now be adjusted, so there is one positive benefit to the incident (globally).
I am not sure how you would legally outfit your water borne carriage with suitable armaments, never mind strengthen it to handle the recoil. A 0.5-calibre firing HE would be quite adequate, but there would need to be at least two, chain fed, with suitable ammunition and manned 24/7 to permit protection before you come in 7.62mm range. Merchant shipping was not armed during the initial parts of war, or later on, because it was not particularly effective. The exceptions being decoy ships with essentially ground based howitzers fitted to put a hole in a surfaced submarine (which surfaced to use their deck gun rather than waste torpedo's). It gets complicated arming ships re rules of engagement, liability, port authorities and so on. Arriving in NJ or London carrying a 0.5-calibre over your shoulder will gain you a lot of interest and not necessarily friendly :-) Then again, if Texas were closer to the shore you might get asked "nice grouping bud?".
Hope they get a good meal soon, none the less.