As part of my night training my instructor got me to head out to sea. As soon as I lost sight of the coastal lights in my peripheral vision I was totally on intruments. No moon so no sight of the surface.
It begs the question. Without an IMCr, would I have been legal, and safe?
If you head out over the sea on a 'grey' (but still VFR) day, there is no discernible horizon. I'm not sure it's THAT much different.