Welcome to Blender Artists!
What a beautiful whale! You’re already off to an amazing start
I have some subjective suggestions, which I’d encourage you to disagree with or disregard, as you’ll eventually know what works best for you:
I’d eliminate the current glow.
Since there’s a suggestion of relatively strong illumination on top of the whale - which I like - I’d recommend adding the appearance of a light source above the water shining through.
This gives an opportunity for some volumetric (or faux volumetric) lighting, which can add a beautiful sense of depth and density to the water while highlighting the whale.
I’d also recommend, in keeping with the current direction of light, having a light (top/left) to dark (bottom/right) graduation (gradient) of light.
I created an example incorporating these possible ideas - using only your image - in GIMP:
And, as you can see, there’s a baby whale now as well - just an idea, but something which could build a bit of a story here - a parent guiding its child toward the light, or something like that
Much of these very same effects can be created within Blender’s render compositor (e.g. sunbeams controlled via a Color Mix[screen/add/overlay/lighten/or softlight mode] nod , directional blur node, RGB color nodes, etc.).
Even the Filter / Blur and/or Defocus node can help you contribute to the sense of being underwater here.
Also, Blender’s built-in Color Management options can also help you further tweak the final result.
I hope at least some of this information will be helpful to you.
I’m sure whatever you wind up with will be great!
Best wishes on your project, and I look forward to seeing more of your projects here at Blender Artists!