During December to March, the lake turns to a vibrant cobalt blue colour. It changes to a colder steel grey colour for April to November. Why this happens is still a mystery. Scientists believe water on the surface becomes warmer in summer. This causes calcium carbonate to precipitate out of solution and allows micro-crystallites of calcium carbonate to form. This results in scatter of the blue wavelengths of sunlight. During winter the lake water becomes well mixed, and the lake water is less clear because of tannins and calcium carbonate particles. The angle of the sun has also been found to influence the perceived colour of the lake. The movement of planktonic life-forms within the lake during the seasons and during the day may also play a part in the colour change.