Abstract: At aproximately 8:30 a.m. on February 8, 2019, three employees (Employee #1 and two coworkers) were working at a ship repair facility, on a dry dock, to conduct the air testing on the void tanks of a tug boat. They were making repairs to an air void tank. Employee # 1 was tending the air line system and disconnected the air pot however the incoming air remained on. Due to the quick disconnect on the hatch, the incoming air was not able to escape the void tank, causing it to over pressurize, resulting in a structural failure on the securing mechanism. When the hatch failed, it created a loud pop noise and popped off the deck a little bit. Employee # 1 was startled and jumped backwards, falling over the properly installed fiber rope guardrail system. Employee # 1 fell off the deck of the tugboat approximately twelve feet to the dry dock below. Coworker # 1 and Coworker # 2 activated the emergency alert system and provided care until Emergency Medical Services arrived. Employee # 1 was transported to the local hospital via ambulance. He received bruised brain, fractured ribs and bruised back vertebrae.