The vast Commonwealth Wasteland in "Fallout 4" is home to many secrets, but apparently, there's even more mystery lurking just beneath the waves.

Recently, one "Fallout 4" player stumbled upon what looks to be a pretty solid structure located underwater, Gamespot reported. The structure in question is, apparently, made out of bronze and appears to be functioning as either an underwater pump or some kind of gigantic filtration system. 

The game does little to indicate that the underwater structure even exists and it's not exactly something that pops up right away as the player had to use Power Armor and Mirelurk cakes, a substance that allows the Sole Survivor to breathe underwater, just to explore the whole thing.

"Fallout" games are known for having a variety of easter eggs, and it's easy to label the underwater discovery as just that, but it does raise a few questions.

For instance, the structure appears to be fairly well-detailed, and given how little the game actually has to offer in terms of underwater quests, it can seem out of place and a lot of effort being put into something that is so out of the way that many players may not have ever discover on their own.

Another reason to at least suspect that underwater downloadable content (DLC) could be coming to "Fallout 4" is another fairly recent discovery of the existence of a harpoon gun in the game, Kotaku reported.

The harpoon gun was discovered by "Fallout 4" player "xxdeathknight72xx" and what's interesting about it is the animation it produces. Apparently, the harpoon comes complete with a bubble animation whenever the player reloads it with ammunition, prompting some fans to speculate that it will soon be part of "Fallout 4" as some kind of a future DLC.

Fans will know if there really is underwater content coming to "Fallout 4" when the game's DLC is released next year.