BRANSON, Mo. — As the duck boat made its everyday tour around Table Rock Lake, a popular, summertime tourist stop in southern Missouri, the skies grew dark and a fierce wind, more than 60 miles per hour, began battering it. Waves crashed against the boat’s sides, as it rose and fell in a brutal chop. Then as stunned onlookers watched, some capturing video, the duck boat, carrying 31 people, suddenly slipped under.
Seventeen people were killed in the accident on Thursday evening, the authorities said on Friday, and seven others, including three children, were taken to hospitals. Officials have yet to release the names of the victims, but said that they range in age from 1 to 70. Nine of the dead came from one family, state officials said; two other members of the family who had been on the trip survived. It was one of the deadliest duck boat accidents in United States history.
Residents around Branson, a showy city that draws throngs of tourists to the Midwest every summer, said the storm had come up suddenly, only a short time after weather officials had issued warnings, and with a shocking ferocity.
“The wind picked up, they gave the storm warning,” Michael Homan, a resident, said, “and then massive, straight line winds came out of nowhere.”
The accident raised new concerns about the safety of duck boats, modeled after the amphibious trucks that the United States Army and Marine Corps used during World War II to carry troops and supplies between land and water, and about whether tourists should be passengers on them. After 13 people were killed when a duck boat sank in Hot Springs, Ark., in May 1999, the National Transportation Safety Board had called for sweeping changes to the way such tourist boats operate.
During the storm that swept through on Thursday evening, there were two duck boats on the lake, and both were returning to land at the time of the accident. “The first one made it out, and the second one didn’t,” Sheriff Doug Rader of Stone County said.
The boat that sank had life jackets, but the sheriff said he did not know if people were wearing them. Of the 31 people on the boat, 29 were passengers and two were crew members. The boat’s captain, who had 16 years of experience on the lake, survived and was taken to a hospital, but the authorities said the other crew member, who was described as the driver, died.
Jim Pattison Jr., the president of Ripley Entertainment, which owns the boat, said the weather was calm when the boat left the dock on Thursday. “There were not any issues and they got out of the water and — and then it hit shortly thereafter,” Mr. Pattison told CNN on Friday morning. “It was almost like a microburst.”
The National Weather Service’s office in Springfield, Mo., issued a severe thunderstorm warning at 6:32 p.m. for southern Missouri, including Table Rock Lake, about 35 minutes before the authorities received the first calls about the sinking of the boat.
Jeff Raberding, a meteorologist in the Springfield office, said that the storm entered the area with wind gusts up to 75 m.p.h., which were followed by heavy rain and lightning.
“We knew there was going to be the potential for severe weather and knew that in advance,” Mr. Raberding said in an interview on Friday morning. “I wouldn’t call it necessarily a microburst because microbursts are usually small. This was pretty widespread.” Also on Thursday, tornadoes swept through Iowa, damaging a warehouse, homes and other structures.
The N.T.S.B. said it would dispatch a “go team” to Table Rock Lake to begin an investigation into the accident. The Coast Guard was also investigating.
Ripley Entertainment acquired the Ride the Ducks attraction in Branson last year. Mr. Pattison, the company president, said this was the first such accident at Ride the Ducks, which was started more than 40 years ago.
“People are supposed to be able to go out for an outing and have a good time,” he said. “We shouldn’t be out there in severe weather. We are absolutely devastated.”
The duck boats are modeled after DUKWs, which brought materials ashore during the invasion of Normandy and hauled howitzers during the landings in Iwo Jima. In the decades since, duck vehicles have been used to transport tourists in places like Philadelphia, the Wisconsin Dells and Branson. In duck boats, passengers sit close to the surface, which critics have said make them more dangerous than a typical boat.
Before Thursday’s accident, the deadliest event involving a duck boat was the 1999 accident in Arkansas, when the Miss Majestic sank to the bottom of Lake Hamilton. The N.T.S.B. cited inadequate maintenance as the cause and ordered duck boat operators nationwide, including the company in Branson, to outfit their vessels with additional flotation devices to help prevent sinking.
The victims on the Miss Majestic drowned after they became trapped beneath the boat’s heavy canopy as the vessel took on water and eventually sank in 60 feet of water, the N.T.S.B. found.
The N.T.S.B. investigation found that the United States Coast Guard had failed to follow its own rules regulating the vessels. The agency’s report said that the Coast Guard had generally displayed a “lack of adequate oversight” and that its inspection of the vessel had been “inadequate and cursory.”
The likely reason for that sinking, according to the N.T.S.B., was that the vessel’s owner, Land and Lakes Tours, had failed to maintain the boat.
The safety board also found that duck boats converted for passenger service lacked adequate buoyancy to stay afloat once they began to flood.
It issued a stern warning to operators of duck boats to fix the problem: “Without delay, alter your amphibious passenger vessels to provide reserve buoyance through passive means, such as watertight compartmentalization, built-in flotation, or equivalent measures, so that they will remain afloat and upright in the event of flooding, even when carrying a full complement of passengers and crew.”
It is not clear whether duck boat operators complied, and the Coast Guard, which regulates duck boats, did not immediately respond to calls seeking comment Friday.
In Branson, 70-minute rides take visitors past notable sights along city streets before plunging into Table Rock Lake. The rides are popular with children, who receive yellow duck whistles that make a quacking noise, and have long been a fixture of Branson itineraries, along with the Dolly Parton’s Stampede dinner show and roller coasters at the Silver Dollar City amusement park.
The boats in Branson were modeled after the military vehicles but built specifically as tour boats. According to an archived version of the tour company’s website, the boats include “modern safety equipment” and “patented safety features that no other DUKW-style vehicle has.”
“So, relax and enjoy this unique experience,” the website said.
John Eligon reported from Branson, Mo., and Timothy Williams and Mitch Smith from Chicago. Karen Zraick, Jacey Fortin, Julia Jacobs, Matthew Haag, Susan C. Beachy, Gabe Cohn and Matt Stevens contributed reporting from New York.