This current high seas piracy problem seems to be all about money. Now that's something we can understand. Apparently, until recently the cost to the ship owners was not high enough to get it on the front pages. But now that they've got our attention, let's take a look at it.
The pirate's business plan fails if the cost of doing business exceeds the expected profit. So we simply need to raise the cost of doing that nasty business. See Popular Mechanics for a summary of the problems and some of the proposed solutions.
In the pre-Depp pirate movies I grew up watching, the pirates who got captured were walked off the plank, keel hauled, or something equally punitive. And today? Watch out for the Indian Navy. Recently it destroyed a pirate "mother ship." See Defense News. Excerpt:
An exchange of fire ensued, causing explosions and the navy ship then used heavy guns. "From what we see in photographs the pirate vessel is completely destroyed," a senior officer said on condition he not be named.
(Side note, Al-Jazeera had helpfully broadcast a tape of the pirates' ransom demand.)
But for non-government ship owners contemporary pirates present a contemporary problem -- capture them and they become a problem for captors' government as they plead for mercy, asylum, etc. Or try to kill them and innocents might die, then the next battle would be in the courtroom of the nearest plaintiff friendly jurisdiction.
So the ship owners are on the lookout for non-lethal deterrents. One low tech item is a net deployed around a ship to entangle attacking boat propellers. See Wired. This type defense was developed at least 5 years ago and would only be useful when the ship is idle -- no help for a slow moving vessels that seem to be prime targets. The government name for this net is "Mark 11 Static Barrier Running Gear Entanglement System."
There are Magnetic Audio Devices which make a lot of noise, supposedly enough noise to deter pirates. See Technology sets sights on piracy which also mentions high pressure water hoses and electric fences (for ships carrying nonflammable cargo).
But the acoustic system may really only provide a temporary defense. The other day pirates captured the MV Biscagua which was equipped with an acoustic defense and a three man unarmed security team. A November 28, 2008 press release from the security company says:
APMSS security team embarked upon MV BISCAGLIA came under sustained and heavy attack from pirates earlier this morning. Reports remain confused however we believe that the embarked 3 man APMSS security team (comprising former British military servicemen) were able to mount sustained, non-lethal, resistance, denying the attacker’s access to the ship long enough for the ship’s operating crew to seek safety below decks and to summon assistance from coalition warships.
Reports suggest that the security team were only finally overwhelmed when attackers gained access to the ship and continued to fire upon the embarked security team.
Therefore, apparently a well defended cargo ship these days has a noise maker, a water gun, and maybe a big Taser. Since these things don't seem to be working they need to raise the cost of the piracy business by employing defenses that wouldn't necessarily fall in the category of "non-lethal." Don't take a water gun to a gun fight.