Page 106 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 3: Search and Survey 85
the location of shipwrecks and these include: the navy; sports divers; people involved in the fishing industry including line fishing, sponge diving, pearl diving, and bottom trawling; and professional divers. The navy keeps records of wrecks for defense purposes, because it is possible for a submarine to hide within the magnetic anomaly caused by a wreck or its acoustic “shadow.” Naturally, this information is usually restricted, although naval Orion aircraft with sensitive magnetic location equipment have been used in searches in Australia for the Pandora, the Koombana, and HMAS Sydney. However, in most cases defense organizations are reluctant to provide detailed information of targets. Sports divers are a source of information about shipwrecks; but unless there is good cooperation between the archaeologists and the divers, this information is difficult to obtain (see Chapter 14). Possibly the most likely source of information about shipwrecks will come from people involved in the fishing industry. Small fish congregate around wrecks which provide food and shelter. Larger fish are predators on these fish and thus line fishing is profitable in the vicinity of a wreck (see Section V.A.4). In places where there are large areas of flat featureless seabed, line fishermen have somehow discovered wreck sites. In the Gulf of Thailand, near the islands of Ko Si Chang, three wreck sites are known in an area of about 25 square miles (Green and Harper, 1983, 1987; Green et al., 1986, 1987). How these sites were first dis- covered is not known, but they exist up to six nautical miles from an almost featureless shoreline in depths of up to 35m and, at most, cover an area of 60 ¥ 30m. This instance of local knowledge illustrates that fishermen can be exceedingly good navigators as the ability to relocate by eye such a tiny point at such an extreme distance is quite remarkable. It also implies that the fishing must have been carried out for a very long time and one must presume that the site was found by chance. It is possible that these sites were first discovered by the trawlers that operate in this area, however, the line fishermen deny this and this is confirmed by the trawler operators. Because trawlers drag their nets across the seabed for many hours, if shipwreck remains are recovered in the nets, the time that the net collected the material and thus the location cannot easily be determined. It is remotely possible that the site was recorded at the time of the shipwreck loss and the knowledge of the site has been maintained by word of mouth.
Similar situations exist elsewhere in the world and, through careful nego- tiation with the fishing community, it is often possible to obtain informa- tion about wreck site locations. In Turkey sponge divers are a very useful source of shipwreck information. In particular, Bass (1974) has used infor- mation from sponge divers to locate wreck sites and this work has been extremely rewarding.