Chickens can swim quite well until their feathers become completely soaked, then they float like a lead brick. Or they can panic at the very start and aspirate water and drown from their terrified flailing. There is no way to revive a chicken who has done so.
With chickens, a pool and a koi pond, we've had some unfortunate accidents along the way. I just wanted to add a little on this as we've (unfortunately) got some experience with chickens & water...
We've saved some that fell in right in front of us (some float and some sink immediately), and we've saved some that had been in the water for a while. If they don't panic and sink, I think the cold can get them sometimes before drowning does. We have had some that aspirated (a little) and drank pool water too, and they have thankfully all have recovered. Some were definitely worse off than others in terms of body temperature and water aspirated.
What's worked for us has been using gravity/very light massage to drain out as much water as possible out of the crop and lungs (upside down for a couple of seconds at a time - not continuously though) grab towels, my multi speed hairdryer and a hot pad, and plan to sit on the bathroom floor for a while drying/warming her up.
I absorb as much water as possible with the towels, and use the warm setting with low speed on the hairdryer, or higher heat/low speed for drying feathers/warming faster but be sure to protect her skin from the intense heat. If she's cold I massage constantly to keep blood flowing as I'm warming her up...legs, under wings, chest, etc.
The worst one I had was one of my tiny slender Modern Games. I didn't think she'd make it as her head/neck was flopping down onto her chest and lolling back and forth, eyes squeezed shut, and she kept stretching her legs out straight behind her. She was extremely cold. Even after she was bone dry she was still very cold....I warmed her for at least an hour with the hair dryer and massaged her the whole time. Once she was dry and able to hold her head up on her own, and legs underneath her I just sat on the couch with the hot pad under some towels underneath her for another hour or so and she was finally able to rest a little. We kept her inside for a day or so since she had been so far gone, but usually we've been able to put them back outside once they're dry and warm, also figuring that the relatively low humidity outside would be good for her.
If they're cold don't let them go to sleep (think hypothermia treatment)....think constant mild annoyance with the massage. I've had one or two of them peck and "swear" at me in Chickenese when I've been treating for cold because I wouldn't leave them alone long enough to just stretch out and fall asleep (die).
I welcome the attitude as to me that's a good sign!
