Difference between a Somali pirate and a innocent fisherman

Pirates often take fishing gear out into the deep waters of the Indian Ocean to help feed themselves, and fishermen from the lawless country often carry Ak-47s for self protection.

But if naval officers see a small boat with long metal ladders lashed to the deck, they say they know for sure the occupants have only one thing in mind.
Fishermen don't need ladders!!!