I'm still puzzled by this problem of pirates boarding big cargo vessels near Somalia...
Sure seems to me it would be easy to ward them off with a small security force on each ship, but maybe I'm unaware of the big picture?
The pirates are approaching in small boats, then they throw a grappling hook into the cargo ship while the crew of that ship sprays them with a fire hose to try to prevent them from boarding.
Here's my suggestion:
The pirates approach and sidle up to the cargo ship. The crew on the cargo ship looks over the side and drops a gallon hefty bag filled with gasoline into the pirate boat, then brandishes a flare gun and asks, "Would you like to see the second part of our new welcoming celebration?"
I think most pirates would decline.