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 ...
It is generally recommended to publish photos on the web in sRGB colour space. You have used the correct export setting.
Ideally you calibrate and profile your computer monitor. But this is a huge topic if you want to know all the details. It will be worth the effort if you earn money with photography or are doing prints and need soft-proofing.
The use of ...