Underwater Cultural Heritage is fascinating because of the mystery of its location underwater, its historical context, and the wealth of information in can provide us. The discovery of an underwater object, a wreck or a ruin makes it possible to dive into the past. It is the memory of a time long before us and sometimes of human tragedy such as shipwrecks and wars. As soon as underwater cultural heritage emerges from the water and is exhibited on land, for example, objects from underwater archaeological sites are deprived of their context and lose some of their meaning. Therefore, in recent years, there have been many efforts to preserve underwater cultural heritage in-situ, and let visitors experience the sites in their original location underwater. This is done through different means, including dive trails, underwater tours for non-divers and underwater museums. For a better communication, the Underwater Cultural Heritage Commission of the World Underwater Federation (Confédération Mondiale des Activités Subaquatiques, CMAS) and three universities of the UNITWIN Network for Underwater Archaeology, which complements the work of the UNESCO Secretariat of the 2001 Convention on the Protection of the Underwater Cultural Heritage, developed, for the first time, underwater hand signals for Underwater Cultural Heritage objects. [ABSTRACT FROM AUTHOR]