The attacks have highlighted a growing crime wave that threatens international shipping, as well as shipments of food aid.
"What's particularly worried us over the last couple of years is the intensity of the violence," says Andrew Linington, a spokesman for the Nautilus seafarers' union in the United Kingdom. "What we've seen is an increasing number of seafarers being held hostage for ransom, the use of things like rocket-propelled grenades. It's gone from what used to be known as 'maritime muggings' -- fairly low-level crime -- to something that's much more nasty, much more organized, and much more violent."
The International Maritime Bureau says pirate attacks are up by 20 percent this year, and the waters off the coast of Somalia are one of the main piracy hotspots.
There's a simple reason why -- countries are responsible for patrolling their own territorial waters, and Somalia has no effective central government.
"Essentially you have a wild west environment out there with no sheriff at all," says Ian Taylor, editor of "Cargo Security International." "It's a very large expanse of water with no real control. So it's quite easy for a pirate operation if they're well organized to set up there, to have a mother ship and to have ships coming off that mother ship. They can track ships, they know lots of cargo ships and tankers are coming through that area, which are ripe pickings for them."
There are international patrols that combat piracy in the area linking the Red Sea to the Indian Ocean, but the area is vast. Ships are limited in what they can do themselves to protect against attack.
Arming crews is one idea, but it's also controversial, Taylor says. Otherwise, ships rely on lookouts and take evasive maneuvers at the first sight of anything suspicious.
"They'll also do things like turn the fire hoses on the pirates," Taylor says. "That's usually a fairly effective method. Fire hoses are pretty powerful so they can flush them away. But if you've got pirates who are determined to attack you and you're on a small fishing vessel, there isn't a great deal you can do."
The rise in attacks is spurring calls for action. The United States and France are drafting a resolution at the United Nations that would authorize governments to chase pirates into other territorial waters.
Linington says it's a positive sign, but he's not holding his breath. He says talk takes time to turn into action, and there are complex legal and diplomatic issues to be resolved.
Still, pressure from the international community can bring results, Taylor says. Piracy used to plague the Malacca Straits, one of the world's most important waterways. But concerted action by Malaysia, Indonesia, and Singapore -- more patrols, better monitoring -- have reduced attacks to a minimum.
-- Kathleen Moore