Scripps Institution of Oceanography

SIO Reference 59-39. A continuing program concerned with the visibility of submerged objects has been in progress within the Visibility Laboratory for morethan a decade. Early experimental and theoretical work provided a basis for predicting visibility by swimmers from instrumental measurements of water clarity. Further investigations, theoretical and experimental, and instrumental developments of many kinds verified and extended the original work and enabled this Laboratory to provide the U. S. Navy Hydrographic Office with an accurate water claritymeter and nomographic charts for the interpretation of its readingsin terms of the limiting range at which swimmers can sight any flat,horizontal object lying on the bottom of the sea.