Crabby Den is one of the (Secret) Locations in Vesteria. It is a deep underwater cavern with various aquatic vegetation that serves as the home for the Crabby population. Near the roof of the cavern lies a few broken bridges tracing a possible civilization.
Going deeper reveals the Crabby nest, which is densely populated with Crabbys. It's a very popular area for players looking to level up due to its small circumference where Crabbys are constantly spawning.
It's reachable from a crevasse in the seabed of Seaside Path, around where the main underwater Crabby spawn is.
Golden Chest: At the bottom of the den, search behind the large pink and green shells to find a small hole, which leads to a cave. Jump out of the water and open the golden chest. When opened, an Old Fishing Rod pops out.