Exclusive to: Shipwrecked.
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 reduces the rate of spoilage of perishable items contained within by 50% (making such items last twice as long). It requires 5 Seaweeds, 2 Vines, and 1 Shark Gills to craft and an Alchemy Engine to prototype. The Sea Sack functions identically to the Insulated Pack from the Reign of Giants DLC except that it can float on the ocean.
As with all backpacks, the Sea Sack cannot be placed in inventory or Chests but can be dropped on the ground and used for storage. Unlike the Piggyback and Krampus Sack, it is flammable and will spill its contents and turn to ash if set on fire. Holding an item over a Sea Sack that is on the ground will give the 'Store' option, allowing the Sack to be filled without equipping it.
Despite slowing the spoilage of Food items by the same degree, the Sea Sack does not work exactly like an Ice Box. It will not stop the spoilage of Ice and Ice Cubes and will not cool a Thermal Stone.
- The Sea Sack could be used as a temporary storage for food in case of the players Ice Boxes malfunctioning due to flooding during the Monsoon Season.
- Alternatively, it can be used as a "sea Ice Box" if the player intends to fish with Trawl Nets multiple times in a row, and the fishing spot is far away from their base.
- Sea Sacks were introduced in the Release the Quacken update.