Historic wrecks are attractive to marine archaeologists because they preserve historical information. For example, studying the wreck of "Mary Rose" revealed information about seafaring, warfare, and life in the 16th century. Military wrecks, caused by a battle at sea, are studied to find details about the historic events. They can reveal much about the battle that occurred. Once in a while there is a discovery of a treasure ship, often from the period of European colonisation. Some contemporary wrecks, such as the oil tankers "Prestige" or "Erika", are of interest because of their potential harm to the environment. Other contemporary wrecks are scuttled (sank deliberately) in order to create reef growth.