• Question: Why is the sea water blue in colour?

    Asked by 977nepk48 to Ed, Kerrianne, Nina, Oli, yoyehudi on 6 Nov 2017.
    • Photo: Kerrianne Harrington

      Kerrianne Harrington answered on 6 Nov 2017:

      It’s because to do with light absorption and scattering. Blue is not absorbed very efficiently by the water. When white light, which contains all the colours, hits the ocean, all the other colours are absorbed. So blue light can make it back to your eyes, so you see blue.

    • Photo: Yo Yehudi

      Yo Yehudi answered on 6 Nov 2017:

      Kerrianne’s answer is great! I just wanted to add that while the sea is very often blue, it isn’t always the case – sometimes there might be something in the sea that affects the colour, and other times if it’s grey and cloudy the sea might be similarly drab. The BBC has an interesting article here: http://www.bbc.co.uk/earth/story/201505226-is-the-sea-really-blue

    • Photo: Oli Wilson

      Oli Wilson answered on 6 Nov 2017:

      I haven’t really got anything to add to Yo and Kerrianne’s excellent answers except to say that, because water reflects blue light relatively well and absorbs the rest, you could quite accurately say that the sea looks blue because water itself is blue. A weird thing to think about, but things are the colour they are because of the light they reflect: water reflects blue, so water *is* blue!

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