Plural electrode method and means for water bottom logging

The apparent electrical resistivities of various parts of a marine bottom are determined by supplying an alternating electrical current to a pair of current supply electrodes and measuring potential differences between pairs of measuring locations. The locations are on a straight line on the marine bottom. There is a fixed ratio between the distance between the locations of each pair and the distance between said pair and the pair of current supply locations. Adjoining pairs of measuring locations have a measuring location in common. A flexible cable for taking these measurements is described. The determined resistivities are subsequently compared with calculated resistivities to determine the compositions and thicknesses of the soil layers of the marine bottom.