been a desert for weeks may be destroyed and washed away completely by
heavy rain.
However, underwater the problems are magnified. Tidal changes, storms
and contamination by anchorage debris have to be contended with while an
excavation is in progress. Decisions to leave an object in situuntil it has been
surveyed and photographed properly have to be resisted. The archaeologist,
whether professional or amateur, should be capable of fixing the location of
his find by reference to pre-determined datum points at the time of discovery
and he should always carry a camera and a scale. This is not to advocate a
policy of snatch and run, but an object or a sample swept away by a spring
tide is of no use to anyone. Working in the turbulent shallow waters of the
reefs of the Cape Verde Islands, I learnt that everyone, professional or ama-
teur, had to be trained to record as they worked. There was often no going
back; at least until the weather changed.
A supply of small sandbags stored close to the excavation are useful to
support or protect an area while seeking additional help or advice but leaving
an object exposed to tidal changes is a matter of good judgment and experi-
ence. Because there is no rule of thumb about when to leave and when to lift,
it is essential that an experienced member of the conservation team should be
a diver. The senior conservator should be aware of the situation underwater
and be prepared to evaluate the natural threats to the underwater deposits,
ensuring that each diver recognised the problems and was properly briefed
and equipped before each dive. Preservation and documentation begin at the
moment of discovery.
Whenever possible, objects should be lifted in a rigid container (not in a
bag) and packed with a representative sample of the surrounding matrix to
limit movement and damage during recovery. A supply of numbered plastic
boxes with attached lids should, like the sandbags, be stored close to the
excavation. If surface conditions are severe, the containers, suitably num-
bered and recorded, can be stored on the bottom until calmer conditions
occur.
Backfilling, to protect a site between working periods requires judgement,
experience and a thorough knowledge of seasonal changes in the area around
the wreck. Once again there is no rule that applies to all sites. Knowledge of
the site and an evaluation of any potential hazards, which might threaten
preservation, are essential. Discussion with local fishermen whose lives
depend on their knowledge of the local area can be very rewarding, particu-
larly in parts of the world where meteorological data is difficult to obtain. Tide
Tables are a useful guide, but it is more useful to calibrate any variations for
a specific site and produce modified and reliable data. In many parts of the
world, tables do not exist or they were drawn up in the dreamtime. It is easy
to construct a tide gauge on a nearby beach and monitor the changes through
8 Chapter 1