Astral Sea (4e)

The Astral Sea is a Dungeons & Dragons plane in the World Axis cosmology from the the 4th edition of the game. It is essentially a hybridization of the original Great Wheel Upper Planes, Ethereal Plane and Astral Plane, serving as both a transitive plane and as a residence for celestial beings.

As its name suggests, the Astral Sea physically manifests itself as a great sea of shimmering starlight and ethereal mists, with other "sub-planes" existing as planet-sized islands floating in the Astral, alongside other various planar detritus. Originally, it wasn't going to look like this, but when the Great Lattice of Heaven was shattered, everything was broken, leaving it in its current oceanic state.