Underwater archaeology is archaeology practiced underwater. As with all other branches of archaeology, it evolved from its roots in pre-history and in the classical era to include sites from the historical and industrial eras. Its acceptance has been a relatively late development due to the difficulties of accessing and working underwater sites, and because the application of archaeology to underwater sites initially emerged from the skills and tools developed by shipwreck salvagers. As a result, underwater archaeology initially struggled to establish itself as bona fide archaeological research. The situation changed when universities began teaching the subject and when a theoretical and practical base for the sub-discipline was firmly established. Underwater archaeology now has a number o