Message in a bottle is an item found on the far south-east end of Waiko. It can be investigated to receive a treasure map, which leads players to Milky Bay.
This message in a bottle is currently visible. (wrong?) Once a message in a bottle is found and when a player has walked near its spawn location when it was visible it will always be visible, unless the message in the bottle or its treasure map is in the player's bank or inventory.