Required Tool: Iron Pickaxe
Blocks: Coral Blocks (not the fans etc)

Swim deep into the waters anf harvest the coral blocks for loot.

Droptable: Sand, Red Sand, Large Shell, Arrow, Gold Nugget, Bone, Seashell, Spice Plant, Glowberries, Iron Nugget, Prismarine Shard, Raw Salmon, Raw Cod, Ink Sac, Shroomlight, Moss Block, Moss Carpet, Raw Copper, Candle, Small Dripleaf, Big Dripleaf, Sea Pickle