Underwater archaeology now has a number of branches including, after it became broadly accepted in the late 1980s, maritime archaeology: the scientifically based study of past human life, behaviours and cultures and their activities in, on, around and (lately) under the sea, estuaries and rivers.[4] This is most often effected using the physical remains found in, around or under salt or fresh water or buried beneath water-logged sediment.[5] In recent years, the study of submerged WWII sites and of submerged aircraft in the form of underwater aviation archaeology have also emerged as bona fide activity.[6]