A new electrical method is proposed for determining the apparent resistivity
of multi-earth layers located underwater. The method is based on
direct current geoelectric sounding principles. A layered earth model
is used to simulate the stratigraphic target. The measurement array
is of pole-pole type; it is located underwater and is orientated
vertically. This particular electrode configuration is very useful
when conventional electrical methods cannot be used, especially if
the water depth becomes very important. The calculated apparent resistivity
shows a substantial quality increase in the measured signal caused
by the underwater targets, from which little or no response is measured
using conventional surface electrode methods. In practice, however,
different factors such as water stratification, underwater streams
or meteorological conditions complicate the interpretation of the
field results. A case study is presented, where field surveys carried
out on Lake Geneva were interpreted using the calculated apparent
resistivity master-curves.