Buried beneath the waves around the British Isles are many lost vessels, each with a number of characteristics that make them archaeologically special. First, a shipwreck provides a watertight (forgive the pun) context. Everything in it was associated with a self-contained, functioning entity at the moment of loss and deposition. Sometimes the identity and background of a wreck will be known from historical sources; otherwise dating will depend on typological studies (of coins, pottery, clay pipes, and so on). However obtained, once a date is established for the site as a whole, contextual association will extend that date to everything it contains. The value of this for checking and refining artefact typologies is unparalleled, with the only caution to be observed being the possibility of later contamination, although proper archaeological procedures should negate this risk. A shipwreck has contexts and stratigraphy, just as any site on land.
An important feature of shipwrecks (unless they attract salvage operations) is that, if conditions are right, everything on board has a chance of entering the archaeological record, regardless of utility or value. Terrestrial assemblages rarely include valuable or reusable objects, for these tend to be retained by their owners or appropriated by others. Most land sites thus contain a preponderance of what was abandoned or discarded. This does not, of course, diminish the value of these finds to researchers, but what was once rubbish tends to dominate the archaeological record, while more useful and attractive items are often lacking. We might be forgiven for assuming that the material most valued by terrestrial societies was broken crockery.
Another skew with land sites is their general paucity of organic items, even though they would have dominated the material culture of most past societies. Even today we use an awful lot of it – just look around your own home. Shipwrecks, and other waterlogged sites such as crannogs, often lie in anaerobic environments conducive to organic preservation, and so help to correct this imbalance.
