Lake Hillier is a pink-colored lake on Middle Island, the largest of the islands and islets that make up the Recherche Archipelago, Western Australia. From above the lake appears a solid bubble gum pink.
Unlike other pink lakes in the world like the one in Retba and the salt ponds at San Francisco Bay, the pink color of Lake Hillier has not been decisively proved, although it is speculated that the color could arise from a dye created by the organisms Dunaliella salina and Halobacteria. Another hypothesis is that the pink color is due to red halophilic bacteria in the salt crusts. That the color is not a trick of light can be proved by taking water from the lake in a container – the pink color can be found to be permanent.