How to edit underwater photos with the free editor Gimp

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Following my blog post which aim was to show the basic techniques on how to take pictures underwater, here are the details of my routine to edit underwater photos. With the open-source editing software Gimp, it is easy (and free) to learn how to edit your underwater pictures to enhance your best scuba diving memories. Even if you couldn’t manage to take beautiful photos, this method may help you to save your favourite shots.

My method to edit underwater photos with Gimp

Using the free image editing software Gimp, follow my step by step tutorial to edit underwater pictures in almost no time.

First, download Gimp for free.

Gimp 1

Below, you can click on my original clownfish picture to download it and follow my tutorial step by step;

Once the software has been installed, start it and open the file of the clownfish picture. You can also open the image directly in Gimp by clicking right on the file.

original clownfish picture

1 – Crop your to improve the composition of your underwater photos

Removing some uninteresting parts of the image can dramatically improve a photo. You can also create a more interesting composition by decentring your main subject following the rule of thirds.

Use the cutter in the toolbox.

You can start cropping your picture while respecting the proportions except if you wish to change the format. Once you have defined the new frame, you can also centre or decentre your subject as you want by clicking on the centre of the picture and holding the mouse.

Press “Enter” and your picture is cropped!

Gimp 5
Gimp 6

2 – Use the magic auto levels tool

This one is the magic trick for underwater pictures. It doesn’t work 100% of the time, but I would say a good 80%.

In the top menus, go to “Color” and then select “Levels”.

Tick the Preview option, and click on the Auto button: the difference is stunning!

In the case of this picture, unfortunately, as the clownfish is orange/red, this colour saturates. So we need to desaturate it a little with the other tools. In some pictures, especially wide-angle shots, you can see red or purple colours appearing in your image, especially if you took it with natural light and no white balance control.

In this case, click on “Edit settings as curves“. You can change one by one each colour curve: red, green and blue. In this case, the red one is the curve you want to decrease on the right side.

edit underwater photos - Gimp 7

edit underwater photos - gimp levels tool

3 – Control the colour saturation of your underwater photos

In the “Color” menu, select “Hue – Saturation”.

In the case of my clownfish picture, I decrease the saturation of the yellow and red colours by -10.

To emphasise the tips of the anemone, I decided to add some saturation to their colour by adding +5 on the blue.

edit underwater photos - Gimp 11
edit underwater photos - Gimp 12

4 – Discover the power of the “Curve.”

This tool is one of my favourite ones. Ideal when you have very bright parts in a picture with very dark parts.

In the “Color” menu, select “Curves”.

By simply clicking on the graph, you can change the shape of the curve. The darkest colours are on the left side and the brightest shade on the right. Here I decrease the brightness of the white stripes of the clownfish. You can also increase the contrast of the picture by making the shadows a bit darker.

edit underwater photos - Gimp 13
edit underwater photos - Gimp 15

5 – Final Brightness/Contrast adjustments

I always prefer to use this tool at the end, only if the picture needs a final touch. I sometimes don’t need to use it after the curve tool.

In the “Color” menu, select “Brightness-Contrast”.

The best, once more, is to play with the settings using the preview to check how each can improve your picture. In most cases, I only add +3 to Contrast, but sometimes I need to adjust over or underexposed photos by a -10 or a +10 on Brightness. This is not the case here.

edit underwater photos- Gimp 16
edit underwater photos - Gimp 18

6 – Save your work

You can now save your picture in any format you like by selecting “Export as” in the “File” menu.

You can now share it on your favourite social media platform!

Gimp 19

Here is the result compared to the original. It’s surprising that in so few steps, you could get such a big improvement!

Adjusting the levels, colours and contrast change dramatically the picture

There are additional improvements you can do to edit underwater photos, like removing backscatter, but it takes time, and I will need another blog post to explain how to do it properly.

Is it something you would be interested in?

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How to edit underwater photos
How to edit underwater photos

Posted by Florine

  1. Hello Florine, this is DIrk Jay from FB, have you tried the following script for gimp ?
    i think the results are really good :

    keep writing 😉


    1. No I haven’t, it’s a specially optimised script for uw pics? I need to try that! will let you know!


  2. Hi Florine, do you know how to get similar improvements on video files? I’ve got some from recent dives in Indonesia but can’t edit them in gimp. Hope you can help


    1. Hi Alistair! I use AVS video editor and I can do some corrections but not as good as what GIMP can do. If you want good corrections on your video, I guess Adobe Premiere Elements could be a way to go, not as expensive as Abode Premiere (for the pros) but still not cheap. Anyway, thank you for this new post idea, I will look into it! 😉


  3. Hi Florine, based on your tutorial, I downloaded Gimp. I have some questions… after you correct something, how do you preview? For example, I cropped. The image I’m left with is so teenie tiny I can’t see it properly. How do you preview after your changes at a size you can see? Thanks!


    1. Hi Nicole, could you maybe join our Facebook group “Scuba diving & Adventure” this way you will be able to share screenshots so I would understand better what’s not working. Cheers!


  4. Ricardo Azevedo July 29, 2019 at 12:10 pm

    Nice post. Thank you.

    You wrote: “There are additional improvements you can do to edit underwater photos, like removing backscatter, but it takes time, and I will need another blog post to explain how to do it properly. Is it something you would be interested in?”

    Yes, very much so!


    1. OK I put this on my to-do list 😉


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