(CNN) -- A luxury cruise ship collided in deep fog with a container ship off Vietnam, punching a hole in the container ship and knocking passengers off their feet, a passenger told CNN Monday.
"The foghorn at the back of the ship had been going off consistently, throughout the morning," passenger Andrew Lock said Monday from Hong Kong about the incident, which occurred Friday morning when the Silver Shadow was about five miles from the coast.
"But there was a certain point in time when the foghorn at the front of the ship suddenly sounded. And it was much much louder. And it caused us to look up. And in fact we looked up straight out of the window. And through the fog, to our horror, we saw this Vietnamese container ship appear, sideways on. And it was as if our ship was perfectly lined up to hit it in the side.
Lock said he and his wife had braced themselves for the impact and stayed upright. "So, it was a horrifying moment. And in less than about five seconds after the ship appeared. We did in fact collide right in the side of it."
In a statement, Silversea Cruises said the Silver Shadow "was involved in a minor incident on March 16, 2012, at around 4:20 GMT as it was approaching the pilot station in Ha Long Bay, Vietnam. There was contact between Silver Shadow and a local commercial vessel. Silver Shadow incurred limited minor dents and guests' safety was never compromised. The ship was fully operational and continued on its course to Ha Long Bay, where all shore tours operated normally."
Lock disputed the cruise line's characterization of the incident.
"It was a major collision," he said.
Deanna Kratzenberg and her husband Wes Harder were in their suite when the collision occurred. The Vancouver couple recalled hearing the vessel's horn blast several times. Then they felt the ship hit something. "It was like a full stop. Just -- boom!" she said.
Lock said he and his wife saw that the container ship was damaged.
"The Vietnamese ship rolled over -- at a 90-degree angle," Lock said. "In fact, we thought it was going to capsize. It then righted itself. And with the forward momentum of our ship, it pushed the Vietnamese ship around, so that it actually came down the side, the length of our ship, scraping along the side as it went. And from that viewpoint, we could see just how much damage had been done to that ship, and it was substantial."
He said he wasn't aware of any injuries aboard the luxury vessel, which had a hole dug in its bow, but said the other vessel was badly damaged.
"We struck the other ship in several places that we could see -- we struck it at the bridge, where they would operate from," Lock said. "We literally crushed the ship inwards. And we also struck the sides of the ship, causing a tear along the side, a vertical tear, quite substantial. And as we passed by the other ship, I personally saw several of their crew members just lying on the deck."
Kratzenberg says she and her husband were not instructed by cruise staff about what to do after the collision. There was confusion in the hallways as passengers tried to figure out what had happened and whether they were safe, she said. "There was a lot of fear," she said. "The people around me were crying...For quite some minutes there was nothing to indicate what the crew were [doing] or what [we should] do."
The couple and Lock say that passengers gathered a few of their possessions and headed to the muster stations.
"The crew was calm, but the passengers -- some were scared, or even frantic," Lock said.
But after about 10 minutes, the captain announced that there was no imminent danger, he said.
As they made their way to the station, Deanna Kratzenberg said she and her husband approached cruise officers and asked them how the collision happened.
Wasn't there radar or some kind of technology aboard that would warn if another ship was close?
She says cruise employees repeatedly answered by saying that the cruise ship "had the right of way." When they kept asking questions, she says cruise staffers walked away.
"I would use the word arrogant," she said. "They were acting as if we had, really, no right to ask the question."
The ship went on to anchor in Ha Long Bay as planned.
"The next day, we went to a nearby port and once we were off the ship we could see how extensive the damage was," Lock said.
Silversea said it will carry out a full investigation into the incident.
The 28,258-ton Silver Shadow was built in 2000. It was refurbished last year and is registered in the Bahamas. It carries a maximum of 382 passengers and a crew of 302. It is scheduled to depart March 28 on a seven-day voyage starting and ending in Singapore, according to Silversea's website. Best available fare is listed as $3,599.
Silversea is based in Monaco and has offices in the United States, Britain, Australia and Singapore.