Ordered to get inside and stay down, Oregon tourist Clyde Thornberg heard the pirates' rifle shots hit the side of the luxury cruise liner — "Pop! Pop! Pop!" — then felt the ship accelerate to escape.

At this Omani port north of the pirate-infested Gulf of Aden, passengers told The Associated Press on Wednesday that the crew of the M/S Nautica warned them of pirate dangers before embarking, then deployed clever and non-lethal defenses to keep the marauders at bay.

Sunday's attack on the nearly 600-foot cruise ship in the dangerous waters between Yemen and Somalia was the latest evidence that pirates have grown more brazen, viewing almost any vessel on the water as a potential target — even a large luxury liner with hundreds of tourists on board.

But the assault lasted only five minutes, and the ship with about 650 passengers and 400 crew members on board sped away quickly and was not seized.

"We didn't think they would be cheeky enough to attack a cruise ship," said Wendy Armitage, of Wellington, New Zealand, shortly after disembarking the ship for a daylong port stop in the Omani capital of Muscat.

During Sunday's assault on the cruise liner, pirates on one of two skiffs fired eight rifle shots at the ship, according to its American operator, Oceania Cruises, Inc. But the captain ordered the ship's passengers inside and accelerated the cruise liner quickly, leaving the pirates far behind in their 20 to 30-foot wooden speedboats, powered with twin outboard motors.

"I couldn't see them shooting, but I heard them hitting the ship, 'Pop! Pop! Pop!"' said Thornberg, of Bend, Oregon. "It wasn't really scary because the captain announced for the safety of everybody to get inside and get down, and by that time he was pouring on the coals to the ship and was outrunning them."

Lynne Pincini, of Australia, said she was heading to a friend's cabin when the ship's captain got on the loud speaker and told people to keep their heads down and stay inside.

"We heard the announcement, and of course we went straight out on the balcony to have a look. It was like a very large speedboat. It was running alongside the boat," she said.

The cruise was on a monthlong trip from Rome to Singapore, a route that took it through the dangerous Gulf of Aden between Somalia and Yemen, where pirates have hijacked dozens of boats this year. Cruises and other vessels have to use the route — the only access for the Suez Canal shortcut between East and West — unless they are willing to add weeks to the trip by traveling around the southern tip of Africa.

At the beginning of the journey, the ship's captain briefed the mostly well-traveled passengers on what the vessel could do to ward off pirates.

One passenger, Alica Moorehead, said they were told the cruise ship could outrun the pirates by picking up speed, aiming high-pressure water hoses at them and using a device that blasts painful sound waves at the pirates to distract them. Such devices can blast sounds of up to 150 decibels, focused on targets several hundred yards away — above the normal pain threshold of 120 decibels.

"We had been reassured that they had these ghetto blasters that could go through them. And we could outrun anything that they had," Pincini said.

Moorehead's husband, Pat, said the ship's crew had even laid out the fire hoses before the vessel entered the Gulf of Aden.

"They had laid out the fire hoses for a high pressure repellant. They never did fire them up, but they were ready for them," said Moorehead, a native of Long Beach, California.

"I will say the crew was very calm. They had prepared for this. Every staff member has an assignment in case of an emergency, and every one of them did it calmly and quickly," he added.

It was not clear what devices, if any, the crew used beyond accelerating. Some passengers on the Nautica said the crew used the long-range acoustic device to ward off Sunday's attack, and at least two passengers described hearing two "boom" sounds after the pirates fired their rifles.

But Oceania Cruises would not comment on specific details of the ship's security other than to say the ship's captain and crew used "evasive maneuvers and took all prescribed precautions."

Roger Middleton, author of a recent report on piracy for London-based think-tank Chatham House, said the non-lethal defense are preferable to having armed guards on board — but their effectiveness is limited. For example, simple earplugs can foil the sound device. .

The ship's speed and difficulty in boarding the ship probably were the reasons why the pirates were not successful, he said.

"Lots of pirate attacks fail ... They will go for anything and keep trying until they get on board," Middleton said. "I think they see these things as how much money they get out of them. And lots Western tourists is very valuable."

International warships patrol the Gulf of Aden and have created a security corridor in the area under a U.S.-led initiative, but attacks on shipping have not abated.

In about 100 attacks on ships off the Somali coast this year, 40 vessels have been hijacked. Thirteen ships remain in the hands of pirates, including a Saudi supertanker filled with $100 million worth of crude and a Ukrainian ship loaded with 33 battle tanks.

Pirates freed a hijacked Yemeni cargo ship and its eight crew members without receiving any ransom after an appeal by local clan elders and regional officials, Somali official said Wednesday.

The ship, released Tuesday night, was seized last month in the Arabian Sea. A Yemeni security official had said the pirates were initially demanding a $2 million ransom to release the ship and its eight-person crew.