X-ray backscatter tomography (XBT) is a relatively new radiographic NDE technology that is unique among x-ray methods by requiring access to only one side of an object. The object is interrogated by a collimated x-ray beam and collimated detectors to measure the Compton scatter signal produced by each volume element. The acquired signal can be directly imaged to represent the density of the material as a function of position. We have investigated several XBT applications that exploit this one-sided capability. One such application is the inspection of large composite naval sonar domes. The current method, radiography, requires not only costly drydocking but also dome removal from the ship. Previously, we have reported on our feasibility study and our development of a prototype dome inspection system leading to the successful demonstration of in-situ dome inspection in drydock [1, 2]. Since then, we have developed and demonstrated an underwater system. The benefits of x-ray tomography can now be realized in the underwater environment.