Is a word with several connotations but here it means vessels that are of particular interest to those working in marine archaeology. Many shipwrecks within the Exclusive Economic Zone of coastal states are now protected sites, particularly the ones within territorial waters, and efforts are being made to give a measure of protection to shipwrecks outside these zones. In the USA such sites are protected by the Abandoned Shipwreck Act (1987); in the UK all diving on shipwrecks is governed by the legal definition of wreck. Most governments issue permits which impose restrictions and obligations on those wishing to salvage artefacts from a shipwreck or to excavate a site. Marine parks and reserves have also been created for the management and preservation of shipwrecks. Unfortunately, in the past, the law was slow to catch up with treasure hunters who, helped by the advances in diving equipment and salvage techniques, have plundered many shipwrecks with little regard to recording their structures.
However, marine archaeologists are not just interested in a vessel's construction and fittings; whenever possible they also want information on its performance and seaworthiness, as well as the cargo it contained, the society on board, the socio-economic and historical framework within which it operated, and the environmental context within which it came to rest.
The most accessible sites are usually those found on dry land but, whether interred or abandoned, vessels in this environment rarely survive well. The timbers of the sepulchral ship at Sutton Hoo, for instance, survived only as a buried print in the soil, and exposed hulls rarely last beyond 250 years. Those that end up in wet or submerged environments generally survive better, their state of preservation depending largely upon the botanical, biological, and chemical content of the water, as well as the dynamics and geomorphology of their resting place. Fresh water is an excellent preserver of wood and other organic remains, particularly if the remains are sealed, as was the case with the wetland boats of northern Europe, of which the 3rd-century bc Hjortspring boat from Denmark is an outstanding example. Some of these, to all appearances, were almost as fresh as the day they were abandoned.
Ships that sink in deep freshwater lakes also survive well. The armed schooners Hamilton and Scourge that went down in Lake Ontario during the Anglo-American War of 1812–14 surprised the world in 1973 when they were found sitting upright on the bottom. Their guns were still in their carriages and their anti-boarding cutlasses were still in their racks; indeed one still had its boat hanging from the davits. Cold also helps preserve structures: the Breadalbane, lost in 1853 while searching for the Franklin expedition, was found in 1980, upright and largely intact beneath the Arctic ice.
Salt-water environments are less conducive to survival, though some are quite benign. The Baltic for instance, which has a relatively low level of salinity and oxygen, is free of the teredo shipworm (teredo navalis) and most other wood-devouring organisms, which is why the great, four-deck fighting ship Vasa survived in such an excellent state of preservation.