Neptune's Shell is an accessory that transforms the wearer into a merfolk when the wearer enters the water. In this state, the wearer has the ability to breathe underwater, swim as if they had flippers, and isn't slowed down unlike normal. The wearer will be transformed back into a player when they leave a body of water.
- When in a body of lava, even with a conjunction of Obsidian Skin Potion, the wearer will not transform into a merfolk. This could be because you can't drown in lava.
- When you are submerged in honey, you will be transformed, even though you are still slowed down. This is probably true because you could drown in honey.
- If both the Neptune's Shell and the Moon Charm or Moon Shell are/is equipped while the player is underwater at night, the merfolk transformation overrides the werewolf transformation.