Lake Retba of Senegal is so pink that it looks like a milkshake in areas, which is a pigment that comes from the existence of an algae in the water called Dunaliella salina.
The algae thrives there because of an extremely high salt content in the water, which reaches 40 percent in some places. This also means that swimmers have an extremely easy time floating in the ten-foot deep lake, similar to how they do in the Dead Sea.
There is so much salt in the water that locals harvest it so there is generally people working there for a few hours each day. The harvesters have to protect their skin from spending hours in the high salinity so they slather on shea butter to protect themselves.
The water changes shades throughout the years and tends to have the most vibrant shades of pink in the dry season, since there is no rainwater to dilute the salinity. This is also a popular time for visitors to the lake.