The Ubari Lakes are some twenty pools of brine fringed with date palms lying in the troughs of the Idehan Ubari, a sand sea in the Fezzan of southwestern Libya, salty enough to float a bather without a stroke, and filled by rain that fell on a green Sahara thousands of years ago, seeping in from under the dunes; they are reached by hours of dune driving with a licensed guide. The lakes sit in a basin between dunes a hundred metres high, and the water table that feeds them is fossil, so they shrink as the aquifer is pumped, and Mandara, once the most photographed, is now a hollow of wrinkled salt and dried mud with its palms dying around it; Gaberoun is the largest that remains, its water as warm as a bath and dense enough to sit in, so that wading out and leaning back the lake holds the body at chest height. Umm al-Maa, the Mother of Water, is the loveliest, and early in the morning before the wind gets up it goes completely still and doubles the palms leaning over it in near-black water.
The families who lived on these shores were the Dawada, the worm eaters, named for the one crop the desert reliably gave them, the lake's red brine shrimp, netted and dried; the shrimp lay hard-shelled eggs that survive years of complete drying in the salt crust and hatch within hours of water returning, which is how they outlast the droughts. The Dawada were moved to new villages in the 1980s and the shores are empty, with the ruins of their mud houses at Gaberoun and a few Tuareg tents for the visitors. October to March is the only window the guides cross the sand sea, when the dune surface is cool enough to drive and walk on and the mosquitoes of the hot months are gone. The Ubari Lakes are the Sahara's old rain standing in the sand, and the desert is drinking it back.