Abstract: On March 23, 2024, an employee was utilizing surface supplied air diving equipment to clean sediment from the inside of an enclosed standpipe water tank with a 24-foot water depth. The estimated water temperature was 53.42 degrees Fahrenheit. Sediment cleaning was performed using a hand-held vacuum/scrubber attached to a 3-inch by 90-foot section of flexible vacuum pipe used inside of the tank. Employee #1 reported to the tender and team lead via helmet radio comms that he thought there may be a leak in the drysuit. The team lead advised Employee #1 to exit the water if he thought there was a leak, however, Employee #1 decided that everything was okay, and the dive was continued. Employee #1 later reported that he felt cold but continued working. At approximately 4:50 p.m., less than one hour into the dive, Employee #1 again reported that he was cold, and the decision was made to have Employee #1 egress the tank so they could switch divers as Employee #1 was too cold to continue working. Employee #1 ascended from the tank bottom by climbing the umbilical. After reaching the surface, Employee #1 was unable to hold onto the egress ladder and due to fatigue, the weight of the diving gear and soft pipe, which became entangled in the umbilical, Employee #1 descended back to the tank bottom. The team lead and tender attempted to rescue Employee #1. The team leader then made the decision to call 911 to report a diver in the water and assistance was needed. It took four people (team leader and three EMS personnel) to pull Employee #1 from the water and up through the hatchway opening. After attempting on-scene life-saving measures, Employee #1 was pronounced dead at the scene. It was later determined that drowning was the primary cause of death.