Camera Culling Mask Background Colour

Hi all,

Ever since I upgraded my project to HDRP, when I deselect a layer from the camera culling mask, I've noticed that the background colour is no longer the colour I specified, but rather, it shows the generic world/fog instead. I've selected "Background Type" to Color and not Skybox, so in theory, it should be showing the "Background Color" below, which is blue.

If you see the screenshot of the ECDIS (a moving map for a maritime ship), you can see that the colour of the ocean is not blue at all. It is a foggy colour, which changes according to the sun (when it's dawn, it's orange, for example).

Before I converted the project to HDRP, this would always be blue, no matter what, as it should be.

Wondering if anyone could point me in the right direction?

Thanks in advance!