Archaeology Underwater: The NAS Guide to Principles and Practice

16 BASICPRINCIPLES – MAKING THEMOST OF THECLUES

• Sites of evidence lost or deposited while using the
  water. Shipwrecks are perhaps the most obvious
  example.


• Sites established on or at the edge of water, which
  are partly or wholly submerged. These often relate
  to maritime infrastructure such as quays, wharves
  or docks.


• Sites built in or over water are rarely completely ac-
  cessible to investigations based solely on dry-land
  methods (e.g. crannogs and pile dwellings).


• Sites that were established on land but are now
  submerged (e.g. the prehistoric sites in the eastern
  Gulf of Mexico or the prehistoric sites which were
  submerged when the English Channel flooded).


• Sites which have continued to develop during a
  rise in water-level. Since the site will progressively
  retreat away from its original location, earlier ele-

ments of its development will now only be available

under water.

The second reason for underwater sites being import-

ant is that clues about the past are often so much better

preserved than on land (figure 4.2). However, if artefacts

are left exposed to seawater they will suffer from natural

processes of decay (see chapter 16). Nevertheless individual

objects that do survive are, to some extent, better protected

from recovery or disturbance by the barrier of water

above them (plate 4.1).

Perhaps the most exciting example of potential pre-

servation on underwater sites is a feature sometimes

referred to as the ‘time-capsule effect’. The clues usually

available on land sites, which are often inhabited for long

periods, do not necessarily give an accurate picture of

what was happening at any specific moment; instead

Figure 4.1 Sites have a place in the settlement pattern of their time. Ships, for example, though very mobile, are still
just part of a worldwide system. (Drawing by Graham Scott)