Lake Hillier is pink because Pink lakes tend to have a striking color due to the presence of algae that produces carotenoids, such as Dunaliella Salina, a type of halophile green micro-algae especially found in sea salt fields.
Once the lake water reaches a salinity level greater than that of sea water, the temperature is high enough and adequate light conditions are provided, the alga begins to accumulate the red pigment beta carotene.