  Underwater Cultural Heritage (CH) sites are widely spread; from ruins in
coastlines up to shipwrecks in deep. The documentation and preservation of this
heritage is an obligation of the mankind, dictated also by the international
treaties like the Convention on the Protection of the Underwater Cultural
Her-itage which fosters the use of "non-destructive techniques and survey
meth-ods in preference over the recovery of objects". However, submerged CH
lacks in protection and monitoring in regards to the land CH and nowadays
recording and documenting, for digital preservation as well as dissemination
through VR to wide public, is of most importance. At the same time, it is most
difficult to document it, due to inherent restrictions posed by the
environ-ment. In order to create high detailed textured 3D models, optical
sensors and photogrammetric techniques seems to be the best solution. This
chapter dis-cusses critical aspects of all phases of image based underwater 3D
reconstruc-tion process, from data acquisition and data preparation using
colour restora-tion and colour enhancement algorithms to Structure from Motion
(SfM) and Multi-View Stereo (MVS) techniques to produce an accurate, precise
and complete 3D model for a number of applications.
