Western Australia is home to a number of extraordinary pink lakes. Lake Hillier is a pink-coloured lake on Middle Island, the largest of the islands that make up the Recherche Archipelago off the coast of Esperance.Site Requires Javascript-turn on javascript!cientists speculate that the colour comes from a dye created by bacteria that lives in the salt crusts. Lake Hillier, Middle Island, WA. Middle Island's pink lake dates back to the journals of explorer Matthew Flinders in 1802.