A duck boat full of passengers capsized on Thursday evening after being caught in a storm in Branson, Mo., claiming the lives of 17 people. Here's a primer on the unusual vehicle at the center of the catastrophe.

What duck boats are

Duck boats are amphibious vehicles that function both on land and on the water. They trace their roots back to the World War II and have become notorious for their involvement in a number of fatal tourist accidents over the past two decades.

Today, duck boats are used used to provide multi-perspective tours of cities and towns located near bodies of water.

Duck boat history

DUKW boats — colloquially known as duck boats — were a military-style amphibious landing vehicle, according to a a Boston duck-boat tour website. The boats were most-famously among the amphibious craft that landed on Normandy beaches during World War II's D-Day invasion.

When the war ended, the U.S. military sold off surplus equipment and supplies. Milwaukee veteran Bob Unger bought one of the DUKW boats and he and a friend began giving tours of the Wisconsin Dells in 1946, launching the first duck boat tour company.

The dimensions of today's boats aren't readily available, but the WWII vehicles they're modeled after were 31 feet long and weighed 13,000 pounds when empty.

In many cities, the tours operate independently, according to CityLab, but in some places, they're run by a franchise like Ride the Ducks. Ride the Ducks was founded in 1977 in Branson (the site of Thursday's fatal incident); the business later expanded, beginning tours in Philadelphia in 2003.

Why they can be dangerous

Although some duck-boat accidents have been the result of human error, authorities and safety advocates have long warned that the boats' structures can make it difficult for passengers to escape in the event of an emergency. .

A 1999 incident in Arkansas where 13 duck boat passengers drowned prompted a National Transportation Safety Board investigation. The probe found, according to the Kansas City Star, that the boat's canopy trapped passengers inside the relatively closed-off vehicle and contributed to their deaths.

The Branson boat also had a canopy.

On land, the size of the duck boats can pose visibility problems for operators, pedestrians and drivers of other vehicles.

Regulations

Duck boats have not operated in Philadelphia since 2016, but while they were in use, PennDOT regulated them on the road and the Coast Guard inspected them for seaworthiness, according to Billy Penn.