Last year, I took a number of vacations which involved cruising, diving, snorkelling and walking on glaciers. Thinking back on those trips, I could not help but notice that water and ice exhibited different colours in different settings. I decided to dive deeper into the colours of water. Finally, here are my findings. Water’s True Colour The colour of an object mainly depends on the colour of light emitted from it. In the case of water its colour is also affected by factors like light source, absorption, scattering, and suspended materials. Absorption by water is stronger for red light, but weaker for blue light. Water is therefore, intrinsically blue. However, this effect is only apparent when the water is reasonably deep. This is why a glass of water appears colourless whereas a big aquarium looks bluish through the thickness of water. Why is the Sea Blue? I did two cruises last year, one in the Caribbean and the other in the South Pacific. Owing to the depth of the wate...