This is also persistent for grass as well. I placed a 2x2 hole in the ground with grass/mycelium covered by water. I covered the hole with an opaque block, set the time to midnight, and the random tick speed to 300. I waited about 10 seconds, set the tick speed to 0, time set to day, and removed the ceiling and the water. The grass/mycelium remained despite being at light level 0 and underneath water at night.
Tanner Thomas
This is also persistent for grass as well. I placed a 2x2 hole in the ground with grass/mycelium covered by water. I covered the hole with an opaque block, set the time to midnight, and the random tick speed to 300. I waited about 10 seconds, set the tick speed to 0, time set to day, and removed the ceiling and the water. The grass/mycelium remained despite being at light level 0 and underneath water at night.