Why underwater photos look green or blue

Underwater photos look blue because clear water absorbs red light first and lets blue travel furthest. They look green when the water is full of plankton, algae or dissolved organic matter, which soak up blue as well and leave mostly green. The two casts look alike but need slightly different fixes.

Blue: what clear water does to light

Sunlight contains every color. Water absorbs the long, warm wavelengths first: red goes within the first few meters, then orange, then yellow. Blue survives longest, which is why open ocean looks blue. NOAA describes the ocean as blue because water absorbs colors in the red part of the spectrum.

Depth is only half of it. Light also travels sideways from the subject to your lens, so a reef photographed from 3 m away at 5 m depth has passed through about 8 m of water. That is why getting close matters as much as staying shallow.

Green: what is in the water

Coastal and fresh water is rarely just water. Phytoplankton and algae use chlorophyll, which absorbs blue and red light and reflects green. Dissolved organic matter from rivers, seagrass and decaying plants absorbs blue too. The light that is left is mostly green, sometimes yellow-green or brown.

You will often see green water in lakes, quarries and harbors, after plankton blooms and on many temperate coasts. Tropical reefs and offshore water are usually blue. The same dive site can switch between the two with season, tide and weather.

Why the camera doesn't fix it

Auto white balance is designed for light in air, where every color is present and only the mix changes. Underwater the red is not just weaker, it is missing, so the camera can only partly neutralize the cast. Many action cameras also cap how far auto white balance will go, which leaves a cyan or green tint.

Which fix each cast needs

A single preset or LUT applies the same change to every photo, so it tends to overcook blue shots and barely touch green ones. Correcting each photo from its own pixels first, then adding a look, handles both. That is how VividSea's Auto color works: it rotates the hue just enough to rebuild red, then sets levels for each channel separately.

Try it on one of your photos with the free underwater photo fixer, which runs in your browser.

How to get less cast in the first place

1. Get closer. Less water between lens and subject means more color and less haze.
2. Stay shallow when you can and shoot when the sun is high.
3. Match the filter to the water. Red in blue water, magenta in green water, none with lights. See red filter vs editing.
4. Use lights or strobes for close subjects. They put back the full spectrum over short distances.

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Common questions

Why are my underwater photos blue?

Clear ocean water absorbs red, orange and yellow light, and blue travels furthest. The deeper you are and the further the subject is from the lens, the less red reaches the camera, so the picture turns blue.

Why are my underwater photos green?

Green water contains phytoplankton, algae and dissolved organic matter. These absorb blue and red and leave mostly green light, which is common in lakes, quarries, harbors and many temperate coasts.

Can a green photo be fixed?

Usually, yes. Green casts need the green pulled down and red brought back, rather than only more red. Per-photo correction handles this better than a single fixed filter.

Sources

• NOAA National Ocean Service, Why is the ocean blue?

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