There Will Be A Flashing On Your Screen when you play either Creative or Survival (Tip: This Happends When You Turn On the "Hide GUI" and when you Turned Off the Animated Water).

Steps to reproduce bug:
1.) Go to Minecraft Settings
2.) Turn Off Animated Water Then Turn On Hide GUI
3.) Go to any of your world. And when you're on your world , it will start to flash or flashing just like the furnace last Versions