The Sea Based X-Band Radar (SBX-1) a floating, self-propelled missile tracking system operated by the U.S. Missile Defense Agency consists of an X-band radar array mounted on a 50,000 ton twin-hull semi-submersible. SBX-1 uses four azimuthing thrusters for propulsion and positioning and the requirement to change-out the forward-starboard thruster waterborne fell to Phoenix International. Working closely with thruster OEM Wärtsilä Defense, the Phoenix team of divers and technicians installed a unique underwater hydraulic trolley system to allow the 25-ton thruster to be moved outboard of the thruster well once separation from the steering pipe was complete. This innovation was required because the semi-sub deck overhang coupled with a shallow Pearl Harbor repair berth precluded a direct yard-and-stay procedure. The Phoenix team was able to remove the existing thruster and, reversing this process, install a rebuilt thruster all within the tight timeline stipulated by the ultimate client. As the thruster work commenced, our client asked if Phoenix could also prepare SBX-1 for and perform an ABS in-water survey (IWS) in parallel with the thruster change-out. Our Pearl City location and Hawaii based team allowed us to answer in the affirmative and we went to work immediately performing waterborne hull cleaning, shell-plate thickness gauging, sea-chest blanking, and visual inspection with an ABS surveyor in attendance. During the inspection our divers discovered fishing net inside the aft-port thruster. They subsequently removed the rope guard, cut away all netting, inspected the thruster seals and re-installed the rope guard. All pre-inspection, inspection and repair work was conducted while the thruster change-out was in-process.