Found when making a tnt cannon on latest snapshot. Went to go inspect some damage the cannon made, and found glow squid when I came back. Likely caused because the world is below the level required for glow squid to spawn. Tested with just a random water source, and still worked.

World Specs: Default Superflat world, structure generating turned off, creative mode, doDaylightCycle set to false. Everything else default settings

Also, sorry for choppy video. Had to make it fit within the 10 MB requirement so I set fps to 15.