It occurs to me that the possibility of power armor entering water might occur. Since it's not just an apparel item anymore, would it behave differently? Will it make you sink like a rock? Will the NBC seals keep it watertight? Will there be a rebreather system installed to not drown in it?

I think our feet would turn into mini jetskis, and we would be able to surf.

Power Armor is generally a self contained environment which is why it protects from airborn toxins etc. As such it SHOULD have its own airsupply. I think however the person inside entering the ocean /lake would sink like a stone.

As far as I know, NBC systems are impermeable to outside particles e.g. radiation, chemical gas, and biological matter ,so it is most likely that they are also waterproof...

The main problem would be the weight though... Would the servomotors in the joint even let us swim? We don't know about that. Even the weight will most likely guarantee the power armor to sink. I think we can't swim in power armor, and may walk in the bottom of the river/sea/lake. Coupled with flashlights, this would be pretty cool like old diving suits, but it might not be cool after some mirelurks are swimming to our direction, ready to shred us while we can't fire our weapons (unless we are using melee, which will be much considerably slower due to being underwater...)

As for the rebreather though, I think the normal model wouldn't have that unless it was modded onto it.

My guess is we can walk to like waist deep, any more and it just blows up.

You'd sink like a stone and could cross large bodies of water by walking along the bottom and then emerge at the other end like those skeleton pirates from POTC. Except with energy weapons and snark. Well, extra snark.

We don't swim, we sink. The helmet acts much like the rebreather from New Vegas and we don't drown because it's recycling our air or takes from an air supply. /theory that makes a lot of sense

That would be really cool if power armor let you breathe underwater but did not let you swim.

I mean that would be fracking awesome and immersive. Not sure if the game engine would be able to handle that in Skyrim you could not implement sinking in the water, you could only affect swim speed.

I think it will be silly if power armor can swim.

If it can walk into water like the old-timey dive suits, that would be acceptable.

It'd be nice if power armor got stuck, or at least heavily bogged down in swamps, and muddy areas hinted at in the concept art.

It'd also be nice if there were places too cramped for power armor use, like some doors to interior areas are too small, and places power armor simply can't go, like, perhaps, the floors of buildings too unstable to hold the weight of power armor.

On the other end, places that require power armor to open stuck doors, lift or move obstacles, survive toxic fumes, and other such that would kill, or prevent an un-power-armor-assisted character from moving forward should also exist.

We already know that you enter in a PA, reather then wear it.

so, maybe you can use light armor with it.

Then PA works like a car. When you want to sneak or swing, you get out of it, do your business and then you return to it and enter again.