The 2nd image is straight from Cycles render output, the 1st one is with compositing and coloring done in external software such as Topaz studio, basically just a few more layers for more bubbles, some sharpening and color balancing.
Its not very clear so im going to work on that, and i plan to perhaps add dome seaweed/plants and some fish, and im going to turn those spheres into mini earths or planets. The 3D shapes were just XYZ math objects i think from a built in addon i have enabled.
Any more ideas are welcome… it will probably take me days to make a fish, as im pretty slow at blender in general.
The basic idea is i added a cube with principled volume shader to make the water and give it a transmissive surface shader as well, then you can drive the volumetric shader with a texture such as an underwater scene with bubbles, and with the correct mapping it will display it in 3D volumetric. I did a thread about how to do this in Blender tests. Wooo hooo! Fast easy hacked smoke/ mist/ fog/dust in blender cycles!