I am trying to figure out how deep underwater you need to go before it is only half as bright as the surface.

Actually, a chart mapping depth to percentage of surface light would be really nice, but I haven't been able to find one..

  • $\begingroup$ Different wavelengths are absorbed differently. So, one could have 50% of 1. number of photons, 2. energy, 3. human perceived 'brightness', all of which are likely different. $\endgroup$
    – Jon Custer
    Commented Oct 16, 2018 at 21:19

1 Answer 1


Is this what you are after??

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From Attentuation of light through seawater


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