Aqua Affinity is a helmet enchant that gives a very useful effect. Without the enchant, it’s very slow to mine blocks while underwater. When wearing a helmet with this enchant on it, you get a buff to that mining speed, one which negates the initial penalty. It basically makes mining underwater the same speed as mining on land. Since it’s a helmet enchant, it can be applied to any type of helmet in vanilla Minecraft.
Combining the Aqua Affinity enchantment with Water Breathing potions makes it easy to mine underwater. This can speed up treks underwater, which is something that pretty much all Minecraft players hate.
But it’s not all upsides. The Aqua Affinity enchantment does not affect the penalty to your mining speed while underwater. You need to be on the ocean floor for the bonus to kick in. Also, unless you’re trying to find tons of Clay, there’s not much reason to use it during normal Minecraft play.
So how do you get it? Of course, you need an Enchantment Table to make this work. There’s no set way to get the enchantment, as it’s all luck-based. Keep hitting the Enchantment Table until you get Aqua Affinity I and you’re good to go. Also, make sure you have the full 15 Bookcases surrounding the table, as that unlocks the full range of enchants.
You can also get the enchantment book from fishing in the water, but it’s a very rare drop. To improve your odds of getting it, get both the Lure and Luck of the Sea enchantments on the fishing pole. These will increase the odds of getting enchantment books from fishing. Due to the high odds against you, it’s probably better to use the table. Sure you will need to spend a lot of Lapus Lazuli, but it’s cheaper than getting multiple rods with two rare enchants on them.