Video and audio recordings from a fatal tourist boat accident in Missouri show that the lake went from calm to deadly dangerous in a matter of minutes.

The National Transportation Safety Board on Friday released information gathered from the video recorder camera system salvaged by divers after the duck boat sank July 19 at Table Rock Lake near Branson. Seventeen of the 31 people on board died.

The recordings show that the lake was calm when the vessel entered the lake around 6:55 p.m.

But the NTSB says whitecaps suddenly appeared at 7 p.m., and winds increased. The captain twice made calls on a handheld radio and alarms sounded. Water began splashing the passenger compartment around 7:05 p.m.

About eight minutes after whitecaps emerged, the video recording ended.

The audio quality varies widely throughout the recording, affecting the intelligibility of what is spoken. Here is a breakdown of the box:

About 18:27:08: The captain and driver boarded the previously empty vehicle. The driver sat in the driver’s seat and the captain sat in the side-facing seat to the right of the driver. (The captain operates the duck on water and the driver operates the duck on the road.)

About 18:28:00: The crew was told to take the water portion of the tour first, by an individual who briefly stepped onto the rear of the vehicle.

About 18:29:13: As the passengers were loading, the captain made a verbal reference to looking at the weather radar prior to the trip.

About 18:33:10: The driver stated a passenger count of 29 and shortly after, the vehicle departed the terminal facility. The captain narrated the tour while the vehicle was in motion.

Starting about 18:50: In the vicinity of the boat ramp, the captain began a safety briefing regarding the water portion of the tour. The briefing included the location of emergency exits as well as the location of the life jackets. The captain then demonstrated the use of a life jacket and pointed out the location of the life rings. The captain moved into the driver’s seat and the driver moved into the seat directly behind.

About 18:55:20: The captain announced to the passengers that they would be entering the water. The boat entered the water. The water appeared calm at this time.

Between about 18:56:22 and 19:00:38: The captain allowed four different children to sit in the driver’s seat, while he observed and assisted.

About 19:00:25: Whitecaps rapidly appeared on the water and winds increased.

About 19:00:42: The captain returned to the driver’s seat. The driver lowered both the port and starboard clear plastic side curtains.

About 19:01:01: The captain made a comment about the storm.

About 19:03:15: The captain made a handheld radio call, the content of which is currently unintelligible.

About 19:04:15: An electronic tone associated with the bilge alarm activated.

About 19:05:21: The captain reached downward with his right hand and the bilge alarm ceases.

About 19:05:40: The captain made a handheld radio call, the content of which is currently unintelligible.

In the final minutes of the recording. Water occasionally splashes inside the vehicle’s passenger compartment.

About 19:07:26: An electronic tone associated with the bilge alarm activated.

19:08:27: The inward-facing recording ended, while the vehicle was still on the surface of the water.

Parties to the NTSB’s investigation are the U.S. Coast Guard, Missouri State Police Highway Patrol, Ride the Ducks, Branson and the National Weather Service.