Fallout 4 contains a harpoon gun, but there’s no way for you to get it. It’s hidden within the game’s files, which could mean that Bethesda have future plans for it or it was deemed surplus to requirement.
A modder by the name of “xxdeathknight72xx” discovered the secret weapon. It leaves a faint trail of bubbles in its wake when a player has it equipped. It’s likely that it’s designed to be utilised in water.
While it’s currently possible to go underwater in Fallout 4, there isn’t much down there. This secret weapon could point to future plans. Who knows what kind of nasties could inhabit the underwater world in the future.
Fallout 4 game director Todd Howard said that upcoming DLC packs will be created based on fan feedback. Whether Bethesda planned to send players underwater or not, they may have to start thinking about what underwater content could be added. It’s quite likely that players will be requesting related content so they can get their hands on the harpoon gun legitimately.
Fallout 4 is now available on PC, PlayStation 4, and Xbox One.