A pufferfish can be caught underwater on Fossil Island. They can be held in a player's inventory to reduce a player's weight by 0.5kg, and can be used via a "Puff" option to restore 15% oxygen to stay underwater for longer.
Using the Puff action produces the message You depuff the pufferfish, restoring some of your puff.. They are then released back into the water as a Puffer Fish which will retreat from the player and appear deflated for several minutes before being able to be caught again. If the player has a fishbowl helmet equipped, it cannot be puffed, stating that You ineffectually squash the poor puffer fish against your helmet..
The Drop action produces the text You release the pufferfish. In this case, it will not be deflated or retreat from the player and can be caught again immediately.
Upon returning to the surface, all pufferfish in the player's possession will disappear.
Attempting to drop a pufferfish above water results in the message The poor pufferfish expires with a lack of access to the sea..
The pufferfish is the only item to provide negative weight while in the inventory; all other weight reducing items only have negative weight while equipped.
Using a carrot on a pufferfish displays the message The pufferfish eats the carrot and makes a strange sound. This is a reference to a viral video of a pufferfish biting a carrot as an involuntary response to suffocation.
