Large size swamp warber seen skulking in a bush along the pools and marshy area. My attention was drown by its call: a warbler like but much stronger "tchek". The bird also did some quite loud "Chrrrrr". Holding itself quite horizontally. Overall upper colour dull cold brown/grey, too cold and grey for Great Reed Warbler and Lesser Swamp Warbler. Too large also for Lesser Swamp Warbler. Long and stout bill. Supercilllium not much marked, unlike Great Reed Warbler. Quite flat forehead. Below white-greyish with visible tawny flanks.