An ocean monument is constructed of prismarine, prismarine brick, and dark prismarine, and is lit by sea lanterns. The monument consists of at least six rooms. These structures are large and pyramid-like. Inside the main entrance, there is a spire that goes up through the monument. At the top floor, there is an elder guardian that acts as a boss, though is not an official boss mob (except on Bedrock Edition). One room has wet sponge covering the ceiling. In another room, eight gold blocks can be found hidden behind a 4×4×4 cube of dark prismarine. The entire ocean monument is guarded by guardians, which are similar to the elder guardian. Even though Ocean Monuments don't have a crafting table in them, there is a Minecraft Lego Set that has a crafting table.
- Prior to the All Together Update, three elder guardians always spawned in each Ocean Monument: one in each wing, and one in the room with the treasure. Currently, there can be up to five elder guardians.
- Once the elder guardians are killed, they do not respawn.
- Once the elder guardians are killed, it's possible to use the sponge harvested from their rooms to completely dry out the inside of the ocean monument, provided one has the coal and time for the operation.
- As of 1.13, it is possible for ocean monuments to spawn under ice in frozen ocean biomes.