Cannons and cutlasses might have kept the pirates of yesteryear at bay.
But not so for modern-day pirates, who troll the seas with GPS systems, satellite phones and rocket-propelled grenades.
As piracy off the coast of Somalia escalates to unprecedented levels, ships are turning to a growing arsenal of high-tech, nonlethal weapons to protect themselves.
Even the sly Jack Sparrow of the "Pirates of the Caribbean" franchise would have a tough time contending with the earsplitting sirens, pain rays and radiation systems ships are starting to deploy.
The number of attacks in the seas off East Africa has doubled in the past year, according to the International Maritime Organization, the London-based United Nations organization charged with improving maritime safety. As of the end of November, the group had received reports of 120 attacks, compared with 60 in 2007.
Maritime experts say that not only have the number of attacks increased, but the modus operandi of the criminals has advanced as well.
But despite widespread recognition that ships are increasingly vulnerable to pirates who attack ships with grenades and automatic weapons, vessels continue to hit the high seas without equally powerful defenses.
"Oil tankers, chemical tankers -- owners and skippers, insurers and legal guys -- no one wants lethal weaponry onboard," said David Johnson, managing director of the London-based MAD International, a distributor of magnetic acoustic devices, or MADs.
International guidelines strongly discourage ships from carrying or using firearms at sea. Deadly weapons could both intensify an already dangerous situation and become additional targets for attackers, a spokesman for the International Maritime Organization said.
Additionally, in some jurisdictions, he said, killing a national may have unforeseen consequences, even for a person who believes he or she has acted in self-defense. Other experts warn that firearms aboard a ship carrying petroleum could damage oil tanks and result in an environmental catastrophe, such as oil spills and leaks.
Litigation and insurance issues also factor into the decision to leave ships unarmed.
"There's no option but to use the best [non-lethal] equipment out there," Johnson told ABCNews.com.
Sound the (Very Loud) Alarm
Many ships are now starting to use MADs and long-range audio devices (LRADs), which can deliver loud and clear sounds to great distances across the water.
Vahan Simidian II, CEO of the Costa Mesa, Calif.-based HPV Technologies LLC and the developer of the technology, said the sound is emitted in focused parallel beams, much like a laser beam of light. As long as you are within a line of site, you can receive a clear, loud sound up to a mile and a tenth away.
His device, based on planar magnetic technology, can be used to hail and communicate with oncoming attackers. It can also be used to emit an unbearably loud noise that can help disorient and delay hijackers.
"I can make your ears ring so bad you can hardly think," he said, adding that though the sound will not knock someone off his feet, it will definitely push him back.
"It could severely hurt your hearing if it was prolonged, depending on how close you get and how long [you're exposed to it]," Simidian said.
In the past year, sales of his devices -- which come in various sizes and could cost up to $18,000 to $20,000 for a ship-appropriate unit -- have grown significantly. In the past year, business has increased by a factor of 12 and he expects it to grow again by tenfold in the next year.
While it's true that simple earplugs could prevent an attacker from experiencing the pain induced by MADs and LRADs, experts say all nonlethal weapons have a countermeasure.
"You can counter pretty much anything you want to," said Jon Becker, president of Aardvark Tactical Inc., an Azusa, Calif.-based firm that provides military and law enforcement units with nonlethal weapons. "The trick is the average Somali pirate is not going to be familiar with them. The goal is to get them to disengage and look for a softer target."
Becker also emphasized that defense systems need to be layered and address the different stages of a pirate's attack: warning pirates as they approach, preventing them from boarding the ship and then dealing with them once the have embarked.
"What you're going to find is none of these individual technologies will solve the piracy thing," he told ABCNews.com.
Beyond Shout and Shoot
Becker said that if hailing or acoustic devices don't deter attackers from proceeding, "impact" weapons -- from launched rubber pellets to stinger grenades -- could be used against them.
MAD International's David Johnson said that entanglement systems, which deploy carbon fiber filaments from a launcher of some kind, are also used to snag the propellers of a hijacker's boat and potentially disable it. As they get closer, powerful lighting systems that use strobe could also be used to hold them off.
"Anything that will attack the senses," he said.
The U.S. military is also exploring another kind of technology that it says expands alternatives beyond the "shout" and "shoot" options: radiation weapons. The Active Denial System, which fires a 6-foot-wide beam that causes targets to feel a painful burning sensation, was originally developed for land use. But, in November, the Navy Times reported that naval forces patrolling the Somali coast are considering using it over water.
Raytheon, the Waltham, Mass., defense technology company that developed the technology, said the Defense Department has concluded that the system could work at sea.
If pirates actually manage to board a ship, experts say, crews could have other tricks up their sleeves. They could employ "direct energy" approaches, such as Tasers, to protect themselves and the ships' cargo.
"Tasers are the newest layer -- the latest thing," Becker of Aardvark Tactical told ABCNews.com.
When somebody approaches, one of the easiest tactics is to shock him with multiple Taser cartridges, he said. Tasers deliver an electric charge that temporarily causes the target to lose neuromuscular control.
Steve Tuttle, the vice president of Taser International, told ABCNews.com that he couldn't disclose exactly where his company's technology was being used. But, he said, Tasers would effectively protect a ship's control area.
"You'd be doing this without deadly force," he said.
Law enforcement and military units from 44 countries use hand-held Tasers that can "incapacitate instantly" someone up to 35 feet away, he said.
'Stuff You Can Buy Out of a Catalogue'
Targets are only stunned while the system is on -- in five-second discharges -- and can be used until the person is safely controlled.
In 2009, Tuttle said the company will unveil even more powerful technology. The wireless eXtended Range Electronic Projectile fires from a 12-gauge shotgun and can be delivered to a distance of 65 feet.
Another innovation, the Taser Shockwave System, deploys multiple Taser cartridges at once and can be activated wirelessly from up to 120 feet away. Stacked vertically or horizontally, the system could create something akin to a force field that makes it difficult for attackers to come within 35 feet of a given area.
While the technology is considered nonlethal, many argue that it is not risk-free. Tasers have reportedly injured, and even killed, their targets. Amnesty International says that, since 2001, more 320 individuals in the United States have died after being shocked by police Tasers.
Michael Lumpkin, a maritime security specialist who served as a Navy Seal for 21 years before retiring last year, told ABCNews.com that though the pirates off the Somali coast have ramped up their technological resources, their gear is largely "stuff you can buy out of a catalog."
Their power lies in their ability to attack ships with speed and surprise.
"The pirate's decision cycle is very fast -- they can change on a moment's notice," he said. "It's cumbersome for the industry to change."