Minecraft wiki entry for Achievement_guide, associated text: When shulkers shoot shulker bullets, move toward the bullet and let it hurt you, then you start to levitate, but you need to take damage of some bullet as a single bullet won't levitate high enough, and make sure there is no block above you. Because you will take some damage from the bullet, it's recommended to wear armor with Projectile Protection IV on all armor pieces. As you will fall down when the effect ends, your boots should be enchanted with Feather Falling IV, or/and drink Potion of slow falling or eat a chorus fruit so it completely negates all fall damage. To Brew Potion of slow falling, you need phantom membrane dropped by phantom which can only spawn after the player has not slept for at least 3 days.