The Isla del Caño lies 17 km. due west of Marenco. The island and its environs invite study from several points of view. It is Costa Rica's largest concentration of coral-building organisms along the Pacific. Schools of tangs, jacks and needlefish present an ever-changing panorama to those who venture below the surface. Boring sponges, Diadema sea urchins, sea cucumbers, many crustaceans and calcareous alga mats and balls add to the variety of life found among the Porites and Pocillopora corals of these reefs.