Aqua Affinity is an enchantment in Minecraft that can be applied to any helmet. It increases the mining speed of blocks underwater, making it equivalent to mining on land. Without Aqua Affinity, mining blocks underwater takes five times as long as mining on land. However, even with Aqua Affinity, mining speed is still decreased when floating in the water. This enchantment cannot be applied to any other piece of armor, weapon, or tool without using commands.