Eevee how to control volume density with precision?

Did my fair amount of searching on the subject but it is older stuff for Cycle but i did try a few node setup but nothing work properly in Eevee.

I want to have control on the fading of a vertical volume instead of the abrupt change you see here ;

I tried a 2d gradient done in Photoshop but as expected it didn’t work because it was not a 3d gradient texture. I also tried with gradient ramp all mode ease, b-spline etc and nothing can make that volume transition more gradual.

Maybe one of you have an idea on how to achieve it?

Can you give us the blend file? It would be easier to examine this that way.

Sure here it is i had to remove ocean surface and floor since it was too big to upload.

underwater_shader_forum.blend (750.8 KB)