The lair of the Crab King. On the surface there is only the well itself: a hole ringed with mangrove roots and mud in the middle of the marsh.

Where

One per world, built at the first start, under the heart of the first Jiangnan Waterlands found more than 800 blocks from spawn (the Jiangnan only grows in the East region, wherever this world put it). Not in flat worlds.

Inside

• A round cavern 88 blocks across, its floor 46 blocks below the marsh, more than 25 blocks of headroom over the whole fighting ground
• The well, 8 blocks wide, with mangrove roots hanging in it and vines to climb back up; under it a pool 4 blocks deep: you can jump in from the surface
• A junk broken in two against the west wall, its stern half sunk in the mud, its bow raised, three masts with torn sails
• Ten nests around the edge; the cavern is brightly lit, so no other monster spawns there

Who is there

The Crab King by the pool, facing the well, and four armored crabs around him. When he breathes his mist here, it fills the whole cavern, floor to vault.