Abstract: At 9:15 a.m. on January 19, 2018, Employee #1 was using a oxy/fuel gas cutting torch to cut a piece of metal being held by Employee #2. Earlier that morning, , around 7:03 a.m., Employee #1, a fitter, and Employee #2, a welder, boarded the William E Strait, a line haul vessel under repair. They found that the gas line for their cutting torch, which had been left inside the vessel in a room below the deck locker near the bow the day prior, had been turned on and a torch was not connected to the line. Oxygen and propylene flowed into the vessel for an unknown period of time. Employees #1 and 2 reported smelling gas throughout the boat. After turning off the gas, the two employees turned on two ventilation fans to remove the gas from the space, where the hose line was located. One was placed at the top of the stairs on the main deck, blowing into the space, and the second was placed in a port hole above the space, blowing outward. They vented the space for about an hour and a half until they could not smell gas anymore and then started work that involved cutting and welding without having the atmosphere tested. Inside of the room adjacent to where the open end of the gas line was located was an open 2,569 gallon potable water tank that was empty, which was connected, via a 4 inch pipe, to a 5,743 gallon potable water tank that was located in a space between the vessel's two engines in the lower engine room near the center of the vessel. Propylene and oxygen from the release entered into the forward portable water tank. At 9:16 a.m. Employee #2 was holding metal that Employee #1 was cutting with a cutting torch in front of the open port of the forward potable water tank, when both tanks exploded. Employee #1 suffered burns and trauma to his body, resulting in his death, while Employee #2 sustained burns to his face and arms, trauma to his body, and ruptured ear drums, which he was hospitalized.