102 UNDERWATERSEARCH METHODS
Hand-held metal-detectors must be used systemat-
ically if they are to be an effective search tool. This
usually entails total coverage employing the corridor
or grid-search techniques as shown in figure 12.3. It is
important that the search-head of the instrument covers
every square centimetre of the area of sea-bed under
investigation. Investigating metal-detector responses by
digging around an anomaly without regard to the other
clues that might be disturbed is not a valid archaeolo-
gical technique. Nor is any approach involving a diver
with a metal-detector swimming in a random pattern
over a site, looking for souvenirs.