Lake Hillier

Fill a bottle and the water stays pink, which is how you know it is alive

Bubblegum pink water, 600 metres by 250, on Middle Island off the Western Australian coast. Fill a bottle from it and the water in the bottle stays pink. Whatever is doing this is in the water, not a trick of the sky, and the current answer is biological, the alga Dunaliella salina together with halophilic bacteria; a 2015 metagenomic survey found Haloquadratum, Haloferax and Salinibacter living in it. The salt is Dead Sea strength and you could swim in it safely, except that you cannot get to it. Matthew Flinders logged the lake on 15 January 1802 and wrote that it was so saturated with salt that enough had crystallised near the shore to load a ship; it is named for William Hillier, a crewman of the Investigator who died on that voyage. Recent rain has diluted the colour and it is expected back as the level drops. You see it from a scenic flight out of Esperance.