Minecraft wiki entry for Achievement_guide, associated text: Brew 3 potions of Water Breathing (Extended). Drink a potion and stay underwater without losing oxygen. Each potion lasts for 8 minutes so you have an extra 24 minutes of water breathing, more than 4 minutes of the goal required. While you're underwater, you can explore underwater caverns, the sea floor, fight drowned, find structures such shipwrecks, ruins or monuments, or build underwater to spend the 20 minutes.