So lets get started I was using the official MC Launcher and activate the current snapshot 17w49b everything was used officially. This test was in laptop. Everything was normal there were no issues while starting minecraft. I start up a flat world and mess around with the debug stick Everything was fine until then here is where the glitch starts. I watched a video by AntVenom seeing you can fly using elytra in water so I create a pond. The flat world have layer of 1.bedrock 2.dirt 3.dirt 4.grass.The pond was 2 block deep.This test was used in creative. I swim using a elytra and I was so suprised it works I mess around about 5 minute and I look some different directions every direction is fine without problem and finally I look up. Then I fell into the water under the dirt and below the bedrock just like I'm nothing but a ghost. Then the game crashed. And now here I am writing this glitch report. I did not open Minecraft again or do anything. I just come here and write this report. No firework was used.