I downloaded your scene, you had the volumetric cloud "opacity" set at 8.2 %, so it was basically invisible.  I guess you played with all the settings, because when I upped the opacity it was pretty much a grey box. Try inserting a default cloud and render it without changing the settings. Don't change the default shader. Create a new shader or use a preset.  Don't use HDRI, Realistic sky and gradient background all at once. Don't move the vertical position of the terrain up or down. You can resize it, but make the vertical position  (z-height) always half of the vertical size ( z-size value). Then put your water plane where you want it. The infinite water plane needed a bump texture, try some of the water presets. Don't turn up the global brightness much in the realistic skies, instead turn up the brightness of the sun light. The reason your cloud settings were so weird was that you made your default shader,  the water shader, then when you created the cloud it was given the default shader. I've uploaded a quick render of your scene with a few of the changes I've suggested. sorry about the plane texture, obviously I didn't have the bitmap texture you used. Only procedurals will be saved withinn the file unless you tell it do otherwise.