Patent Number: 
Section: claims

1. An apparatus for inspecting an underwater pipeline to determine wall thickness or information about contents of the underwater pipeline, the apparatus comprising:a gamma radiation source;an array of detector units;a data processor, and,a buoyancy material,wherein the gamma radiation source and the array of detector units are mounted to enable an underwater pipeline to be interposed between the gamma radiation source and the array of detector units so that gamma radiation emitted by the gamma radiation source passes along a plurality of paths through a portion of the underwater pipeline and impinges upon the array of detector units,wherein the data processor is configured to acquire data at a plurality of radially offset positions around the underwater pipeline to acquire density data at a variety of angles through the underwater pipeline when the underwater pipeline is interposed between the gamma radiation source and the array of detector units in order to produce a representation of the underwater pipeline or contents of the underwater pipeline using the density data. 2. The apparatus according to claim 1, wherein at least one of the gamma radiation source and the array of detector units are rotatable around a circumference of the underwater pipeline when acquiring data. 3. The apparatus according to claim 1, further comprising a hinged housing that is configured to be opened and closed around the underwater pipeline. 4. The apparatus according to claim 1, wherein the representation is a representation of a composition of the underwater pipeline or the contents of the underwater pipeline. 5. The apparatus according to claim 1, further comprising a tomography algorithm for building the representation of the underwater pipeline or the contents of the underwater pipeline.