The stretch of water, dubbed the Lac de Gafsa, may be the result of a rupture in the rock above the local water table. The lake appeared in the Tunisian desert like a mirage; one minute there was nothing but scorching sand, the next a large expanse of turquoise water. Shepherds discovered the lake, thought to be up to 18 meters deep and covering one hectare, three weeks ago. Local geologists suspect seismic activity may have ruptured the rock above the water table sending the liquid to the surface.