Fallout 4 isn’t like any other Bethesda game. It’s got a well written story for once, and the locations you can explore throughout the world are far more diverse than anything the studio has made before.
Some of the things they’ve hidden in the world, for adventurous players to discover, are underwater locations. You’ll only find these if you dive deep beneath the waves. It’s really easy to miss these places if you don’t have the Aquaboy or Aquagirl perk, and on top of that, they aren’t readily marked on your compass, so you’ll have to go out of your way to find them.
As for the rest, you can find them in the map below.