The professionals, namely the crew of cargo ships, avoid having guns on board, even when their route takes then to pirate-infested waters. (They also avoid having girls on board.)
I think that was the case until a few years ago. Nowadays, Reuters reports, cargo ships have "massively" increased the number of guns on board along with people who know how to use them:
"Like many merchant vessels, the QM2 now carries armed private contractors when passing through areas of pirate risk... M-16-type assault rifles and sometimes belt-fed machine guns...
For many in the shipping industry, the fall in attacks is a vindication of the decision to massively ramp up the use of armed guards. So far, not a single ship with armed guards has been taken by pirates..." http://www.reuters.com/article/us-somalia-piracy-idUSBRE91B1...
