It's Lake Retba, in Senegal, west Africa. It's high salt content means that people float much higher in the water than normal. The COLOR is caused by the very high salt content, up to 40% in places. If this answer is correct, please open the next challenge to any who wish to participate.
The colour is caused by algae (Dunaliella salina), and the name is Lac Rose.
Thank you!Spot on Johanna! Over to you!!