FILE PHOTO 7OCT96 - A research diver inspects the floor of the Mediterranean between Monaco and Cap Martin which, since 1991, is covered in more than 30,000 hectares by a weed "Caulerpa Toxifolia" which destroys marine life, leaving nothing but a barren green bottom to the sea. Researchers have recently discovered a species of leeches which feeds from the chlorophyl in the toxifolia and may provide a solution to this particular ecological problem.