It's been implied that at least some of the bodies of water around Eorzea will be explorable via swimming as of 4.0 - mostly for the sake of general enjoyment but also for quests and gathering.

Gathering equals the acquisition of items, which in turn means item descriptions. I guess it's pretty minor in the grand scheme of things but I can see some of those descriptions shedding light on some pretty intriguing stuff. Perhaps we will be able to swim around the area surrounding the Wanderer's Palace and gather items that sheds further light on Nym?