Ocean Ruins are underwater structures that generate in ocean biomes, with rare occurrences on beaches. They appear in two variants: cold ruins, made of stone bricks and gravel, and warm ruins, made of sandstone and sand. Both types can generate as small huts or large complexes, and often appear in clusters.

These structures frequently contain chests with loot such as coal, wheat, gold nuggets, buried treasure maps, enchanted books, fishing rods, and armor. Large ruins have slightly better loot than small ones. Suspicious gravel in cold ruins and sand in warm ruins can be excavated with a brush to uncover archaeological items like emeralds, pottery sherds, iron tools, and sniffer eggs.

Drowned mobs commonly spawn in and around the Ocean Ruins. Loot chests are sometimes buried beneath blocks, requiring excavation to access. Some Ocean Ruins are partially or fully buried in terrain such as sand, gravel, or even stone.

Ocean Ruins are valuable for early-game loot, archaeology, and locating buried treasure. Their variety in size, shape, and material makes each Ocean Ruin unique and an interesting point of exploration in the ocean.