The Sea Sack is a backpack introduced in the Shipwrecked DLC, used to expand the character's inventory. While it has only 6 inventory slots, it slows the spoilage of contained within. It requires 5 Seaweeds, 2 Vines, and 1 Shark Gills to craft and an Alchemy Engine to prototype. Sea Sacks function identically to Insulated Packs from Reign of Giants. Despite slowing the spoilage of food items, the Sea Sack does not completely work the same way as an Ice Box. Unlike the Box, the Sack will not stop the spoilage of Ice and Ice Cubes and will not be able to freeze a Thermal Stone.