Ocean Monument

The Ocean Monument is a towering prismarine temple on the sea floor defended by guardians and three elder guardians. It generates in the Overworld, across 4 biome types - Deep Ocean, Deep Lukewarm Ocean, Deep Cold Ocean, and Deep Frozen Ocean - which makes the Ocean Monument moderately uncommon to come across as you explore.

Height-wise the Ocean Monument sits in the Y 30 to Y 60 band, which narrows down where to look. Monuments generate only in the deep-ocean biome family and are widely spaced, so they sit far apart. An Ocean Explorer Map from a cartographer villager points to the nearest one, and the large dark silhouette is often visible from the surface in clear water.

It was introduced in Minecraft 1.8, and the detail that defines it at a glance is simple: large underwater prismarine structure.

On Java Edition the quickest method is the command /locate structure minecraft:monument, which prints the coordinates of the nearest Ocean Monument and the distance to it.

Without commands, head for one of the Ocean Monument's biomes (Deep Ocean, Deep Lukewarm Ocean, Deep Cold Ocean, and Deep Frozen Ocean) and search the Y 30 to 60 band. Because it is moderately uncommon, you will usually pass a few biomes before a Ocean Monument appears.

Use /locate structure minecraft:monument. Found in deep ocean biomes. Buy an Ocean Explorer Map from a cartographer villager. Large dark structure visible from the ocean surface with guardians swimming around.

Once inside, there are no ordinary loot chests. The fixed reward is a treasure room containing eight blocks of gold, plus the sponge rooms that may generate; elder guardians also drop wet sponges and have a chance at the Tide armour trim template.

Some rewards here are guaranteed every time: Gold Block (8) and Sponge (1-30). Those are not random rolls - the Ocean Monument always provides them, which is a big part of why it is worth seeking out.

Among the Ocean Monument's randomised drops, the most common pulls are Prismarine Shard at about 80%, Prismarine Crystals at about 40%, Raw Cod at about 40%, and Tide Armor Trim at about 17%. At the other end of the odds sit the jackpot items: Tide Armor Trim at roughly 17% and Prismarine Crystals at roughly 40%, so opening multiple Ocean Monument chests pays off over time.

What makes the Ocean Monument genuinely worth the trip is a set of exclusive rewards you cannot get reliably anywhere else - Sponge and Tide Armor Trim Smithing Template - so this is the place to come for them.

Expect to face Guardian and Elder Guardian here, sometimes more than one at once.

The specific hazards to plan around: Mining fatigue from elder guardians (slows mining by 99.7%) and Guardians shoot laser beams. There is more to watch for too - drowning risk underwater, three elder guardians to defeat, and must fight underwater - so do not rush.

The structure is a multi-level prismarine fortress lit by sea lanterns, with dark-prismarine inner chambers, side wings, and pillared halls. One core room hides the eight gold blocks behind a dark-prismarine casing, and one or more sponge rooms may branch off the interior.

Other things you will notice as you explore: elder guardians as mini-bosses, gold block treasure room, and dark prismarine inner chambers.

Each ocean monument contains exactly 3 elder guardians. Defeating them removes the Mining Fatigue effect. The gold room contains 8 gold blocks. Sponge rooms may or may not generate. Ocean monuments are popular for guardian farms, which are one of the best XP farms in the game.