How to Activate a Conduit in Minecraft

Find a buried treasure map. They are found in shipwreck or ocean ruin chests. In ocean ruins, you usually have to dig around to find the chest while avoiding the drowned that guard it. In shipwrecks, the map chest will be in a room with a door.

• Keep an eye on your oxygen bar so that you don't drown.
• Shipwrecks have a guaranteed treasure map while only 43.5% of ocean ruin chests will contain one.

Dig for buried treasure. Travel around until you arrive at the red X on the map. Position yourself so that only a few pixels of the white arrow are visible below the x. Then, dig straight down until you find a chest. Inside, there will be many valuable items like TNT, gold, and diamonds, but you're here for the heart of the sea which is used to craft a conduit.

• If you're having trouble finding the X, remember that upward on the map is north while rightward is east. Press F3 to obtain the cardinal directions.

Obtain 8 nautilus shells. These can be dropped from drowned or obtained as a treasure drop from fishing.^[1] As of the 1.16 Update, the fishing rod needs to be cast into an open body of water (5x4x5) to catch treasure items. Having the Luck of the Sea enchantment on your fishing rod helps the drop rate. Drowned have a small chance to spawn holding a nautilus shell in their hand which will drop if you kill them.

• Wandering traders can also sell nautilus shells for 5 emeralds each.^[2] On average, they spawn every 10 Minecraft days.

Craft the conduit. The heart of the sea goes in the center of the crafting menu, with the nautilus shells surrounding it.

Get prismarine from an ocean monument. Dive quickly down to the tallest section of the monument and mine at least 16 blocks of prismarine. If you want the radius of your conduit to be larger, you can expand it, but you'll need to gather extra blocks. Bring a few milk buckets in case you get inflicted with Mining Fatigue.

• Dark prismarine, prismarine bricks, prismarine, and sea lanterns all work.
• To help avoid the guardians, drink a potion of invisibility and take off some of your armor.
• Make sure you don't drown. Bring some doors or drink a potion of water breathing.

Build the base layer using 9 blocks of prismarine. Choose a location deep underwater. Remember, you can use any type of prismarine and even sea lanterns. The pattern used in the picture is just to make it easier to see.

Add a four-block tall pillar to each end of the base. You can stop here for the smallest possible conduit or continue building. The range of the conduit extends 16 blocks for every 7 blocks of prismarine added. Once you get to the maximum of 42 blocks in the frame, the conduit will also attack hostile ocean mobs.

Finish the top of the frame. This will take you five blocks.

Add 12 prismarine blocks that connect the middle of each pillar. In the picture, these are the prismarine bricks.