NoFall

No Fall prevents you from falling a specified distance. For example if you're about to fall into a deep ravine, No Fall will stop you from moving off the last block and falling down the ravine. It will prevent you from falling even when running, jumping, or being hit off. With this mod, you can run around the top of a mountain, far above ground, or explore the End without worry about falling to your death. No Fall can also be set to prevent you from falling into lava or water. Settings can be changed using commands.