It must be a strange thing for developers designing any open-world, as although they're crafting mountainsides and entire townships, it's not complete without some underwater areas... that hardly anyone ever actually sees. GTA: San Andreas was one of the first to really make deep-sea diving a 'thing' (which GTA V would then design missions around) and The Witcher 3 contains a story-centric quest that sees you plumbing the depths of the abyss for some specific information. On Fallout's end though, all that vast blue yonder is optional - although intrepid fans have found all sorts of what looks like abandoned structures and debris, a secret Power Armour frame, and a lot of discarded items that look as though missions could be set amongst them. PC users uncovered code for a harpoon gun in the game's files, too, and as Power Armour can already be used underwater, it's practically a given.
