When I type /gamemode 0 into the chat box to switch to survival from creative, if I flew up to a height that I die from if I fell, unless I am on the ground, I die as if I took all the fall damage from that fall.
I had an awesome world until I lost all my items after coming out of a huge cave system.

Recreation:
1. Set game mode to Creative.
2. Fly up to a height that makes the ground all foggy on tiny or short distance.
3. Descend to around three blocks from the ground.
4. Type the command for survival mode, and the bug will occur.