This is super cool, the Washington State Ferries posted this today on their various social accounts:
"The M/V Tacoma was recently taken out of service due to a stern tube seal issue. Thurs. (1/8), Global Diving installed an underwater habitat on the vessel. It was sealed to the hull & around the propulsion shaft. By pressurizing the habitat w/ air, crews removed water from the area.
This created a dry repair environment. It allows repairs to be made to the damaged seal w/o requiring the vessel to be dry-docked. Global Diving is working in coordination w/ our maintenance teams to complete repairs & return Tacoma to service as safely & quickly as possible."
Really clever. Wouldn't want to be the one working in there myself, but each to their own.