I've been there too in my PA, walking along the sea bed. I found that glitch where the underwater effect disappears and I noticed the pipelines and how much effort had gone into designing the sea bed across the whole bay, so I kept walking to see if there were any treats to find. But after a while I hit some kind of invisible wall where my PA no longer protected me and I suddenly drowned. It's certainly a place where a hidden faction could be found in later content for just $29.95.
Theres a couple of things underwater but nothing remarkable. everytime I swim though I feel like I'm going to be eaten by one of those dolphin sharks or something. but there really isn't anything awesome underwater as I would hope.
They're was going to be some underwater related content, there's still a Harpoon Gun in the game files that was designed to be used in underwater combat (it leaves a trail of bubbles in it's wake when fired anywhere) and there was the cancelled quest "20 Leagues Under the Sea" the icon of-which showed the Vault Boy in somekind of Bathysphere.
What-ever it was going to be about though is unknown, but you can tell from the actual effort in-places underwater that something was intended to occur.
Cool. I need to get my Power Armour on and take a walk underwater.
oooh! A harpoon you say? any vids or pics of it?
An underwater city DLC would be cool.
Now I need a Mr. Bubbles suit of power armor.
And that just sort of reminded me of that one traveling merchant...
I think this city could be like a sort of mix between: a vault, rapture and a biodome. or with a lot of bases build between rocks and the same ocean.
A submarine mount and a quest to find a mutated Nessy monster would be immense.
More underwater and maritime oriented DLC would be amazing. An undersea lab may work, or maybe a Titanic sized boat as a DLC location. All I really want is a quest where we have to walk the ocean floor in Power Armor. I so wanted to walk the ocean floor in Bioshock, but no dice... maybe they could add waterbreathing mods to Power Armor for people that don't have Aquaboy, or even give us deep-sea exploration power armor. That might be a bit too much like Bioshock, though...
I'm still waiting on a Ghoul captain Ahab that's hellbent on finding the mutated radioactive sea monster what ghoulified him.