Crabby Den is one of the locations in Vesteria. It's a very popular area for players looking to level up due to its small circumference where crabs 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. Currently, it doesn't give you anything, but it used to give you an Old Fishing Rod.