Is Bethesda hiding something in Fallout 4's oceans?

Fallout 4 players are scouring the ocean floor and lake beds in search of hidden treasures.

How much time have you spent underwater in Fallout 4?

One Redditor happened to fall in the ocean and couldn't easily get back out, so took the opportunity to explore a little using their Power Armor's oxygen reserves. They then uploaded a beautiful Imgur gallery of their adventures.

Although there don't seem to be any quests related to it, there are some lovely, detailed environments underwater. While this particular little jaunt didn't turn up much of note, there are plenty of things to find underwater across the Commonwealth, including Power Armor frames, ammo caches, a submarine and more.

The question is: is that all there is, or are there more secrets to find? Why are there so many different ways to survive underwater if there's nothing of note down there? Does the secret harpoon gun mean we can expect our first DLC adventure to take place on - or in - the briny blue?

Keen to go have a look? While Power Armor provides a few minutes of exploration at a very slow pace, you can trot around much faster if you use Mirelurk Cakes or the Aqua Boy/Girl perk. You'll also want plenty of protection from radiation if you don't take the perk route.