Lac Rose is a pink lake worked by hand, thirty-five kilometres northeast of Dakar. It is three square kilometres of water barely three metres deep, held off the Atlantic by a single strip of dunes, and some 3,000 collectors stand chest-deep in it every day. They rub shea butter into their skin against the brine, break the crust off the lakebed with a pole and scoop it by basket into pirogues painted in Senegal's colours. Women carry the loads ashore to the white mounds along the dunes. The water is up to 40 percent salt in places, saltier than the Dead Sea, so wade in and it holds you up whether you want it to or not. The colour comes from an alga, Dunaliella salina, which packs its cells with the orange pigment that colours carrots when salt and sunlight press it hard enough.
The colour is not a fixture, and the lake nearly lost it. In August 2022 a drainage channel was cut to push floodwater out of Dakar's swamped suburbs. Torrential rain then burst the lake's banks, and enough fresh water arrived to thin the brine past the point where the alga could work. Retba turned green. Seven thousand tonnes of harvested salt washed away, and for months nobody could dive the bed. Pumps hired by hotel owners drew the excess water off in 2023, and in 2025 researchers at Cheikh Anta Diop University confirmed what the boatmen could already see: the pink was back. It runs strongest between late January and early March, deepening from pale rose towards strawberry. Even now nothing is settled here. Unsewered hotels and unplanned building have pushed nitrates far past safe levels, and the dunes are being mined for sand. That is the same narrow strip you cross to reach the Atlantic, and the only thing keeping the ocean out of the lake.