This adds close to realistic survival experiences for Minecraft. Currently, it adds the following
Thirst Mechanics - You now have a need to drink water. The amount of water you currently have in your system, your thirst, will be displayed on the screen above your hunger and if your thirst falls to zero and you don't drink water you'll die of dehydration. You can get water by crouching and right-clicking a source block of water or drinking a bottle of water, but if you want to avoid the thirst effect smelt the water bottle to get purified water or drink a potion
Temperature Mechanics - Your body temperature will be influenced by how hot or how cold your current biome and the blocks around you are.
Sleep Mechanics - You will now require sleep to function. If you spend your days without getting sleep, your body will start to shut down, and the more time you spend awake, the more the debuffs will pile up
Stamina Mechanics - All actions you perform in your world will now cost energy to execute. This energy can be replenished by not doing anything, taking a walk, or just laying in bed. Sleeping fills the meter up to the limit. When you run out of energy, the meter will turn red. This is your reserve energy and is a clear indicator that you will die if you work your body anymore. Once your reserves run out, You will swiftly proceed to die.
Each and every mechanic can be disabled in the config file.
Upcoming Mechanics (May not actually be implemented):