Water does not disappear when poured into the void in the end.
When I was building something in the end between the end islands and dragon island, I ended up accidentally having water pour down into the void, and about 30-40 minutes later I noticed a small column of water just floating in the void between Y = 7 and Y = 0. No idea if it’s a glitch, intended, or just a visual bug, but there are real water blocks there, not just ghost blocks.