Abstract: At 5:15 p.m. on May 7, 2019, an employee and a coworker were power washing the fourth level of the sonar dome, a dark, confined space, in the USS John Warner 785 submarine. The employee and coworker were working back to back, about 10 feet apart. The coworker turned around and noticed the employee was not there. The coworker asked another coworker, the tank watch, if the employee had left the area and was told no. The employee stepped through a 2 by 4 foot unguarded access hole in the work platform and fell 20 feet from the fourth level through openings in levels 3, 2 and 1, to the bottom of the vessel. The employee was found unconscious, face down in a puddle 3 to 4 inches deep of pressure wash runoff water. The employee was revived and was able to walk to the Vertical Payload Tube, where he was retrieved from the space by crane. The employee was hospitalized as a result losing consciousness, a gash to the back of the head, and pneumonia from the inhalation of water.