Underwater: Edit and Join separated layers smoothly

Question

As I really enjoy underwater photography, I am wondering how does one end up with a final image like the one I share below:

Unedited on the left, desired effect on the right:

_{Source: https://www.instagram.com/p/CApGLcCHStN/}

This edit seems to complex for Lightroom as it doesn't have a Channel Mixer so I presume the photographer used Photoshop or GIMP. There one can copy a blue/green channel and convert it to red.

In this case, it seems that the photographer is using two separate layers and adds the people separately, so that he can get a darker background.

Assuming that to get an image like the one shown above the photographer is not only using a pure picture and color grading, but editing multiple layers of underwater images and join them smoothly, how does one edit and join edited layers, from underwater images, in a subtle way?

Answer 1

Is this only pure picture and color grading?

The image has obviously been heavily edited in Photoshop or similar.

• The background has been entirely replaced.
• Part of the diver's shirt has been removed.
• The luminosity of the fins has been altered.
• The colors in the final image have very little hue variation.

How does one end up with an image like the one shown... ?

The Channel Mixer is unlikely to be useful in this case. Techniques involved likely include:

• "Hand coloring." – Try using color layer blending.
• Background replacement. – Try using layer masks.
• The usual essential photo editing tools: levels, curves, cloning, layer blending, masks, etc.

Writing a tutorial covering all of these techniques is overly expansive. There are plenty of tutorials online. Consider asking Google or YouTube.