The Site comprises a series of “turloughs” or seasonal lakes fed by springs and a partly subterranean river. It is surrounded by mixed woodland and lies within a larger wetland complex of lake and river habitats together with species-rich grasslands and yew woodland. It is the only site in Ireland where the transition from turlough to climax woodland can be seen. Wetland wintering birds using the Site include numerous nationally threatened species such as the northern lapwing (Vanellus vanellus) and the whooper swan (Cygnus cygnus). Notable mammals include otter and pine marten. The Coole-Garryland complex is also home to one of the most important and unique assemblages of insects in the country, including several notable species of beetles and flies. The nationally rare mudwort (Limosella aquatica) and dropwort (Filipendula vulgaris) are also found, and it is the first known site in Ireland for the water-starwort Callitriche palustris, which was recently recorded there. The Site is important for education and recreation, and for its cultural and spiritual values. The main threats to its ecological character stem from agricultural activity.