Hey all,
First off let me say i have no idea where the nearest vet capable of checking out a turtle is. I asked a few vets and most of them said good luck.
Anyway, here's the story. 
I ended up with a small RES a few months ago. When i got her she was a little under an inch. About 2 months ago or so she started swimming lopsided, then having problems diving, now she hasn't been to the bottom of the tank in some time, it's no longer lopsided, but she can't get her rear end under the water. Right before the lop-sided swimming started, she went from being calm and interested when i approached the tank to skittish and hiding.
This has been about two months of this, her appetite isn't effected at all. She's always hungry. The water temps are the higher side of mid 70's with high end of 80's under the light. Another thing i've noticed is she tends to go through spurts of shedding a lot of skin at once. I thought this was from having the water temp too high, so i lowered it back to mid 70's gradually and it hasn't really changed much. She still basks, but spends most of the time in the water if there is anything moving at all in the room.
I'd like to help her however I can to get better. She's a fighter and a survivor as she's still active, eating, and forever trying to find a new way under the water. She even tried swimming upside down, and walks upside down under her dock.
The only thing i thought may help was to dry dock her for a few days (soaking once or twice a day for a half hour to drink/eat). I was thinking that she must have fluid in her lungs for there to be a buoancy issue, and putting her in a drier area might help to get some of the fluid out.
Any tips on any of this? Even on just to setup a dry tank, if anything is needed would be greatly appreciated.
