If you're thinking of the same picture I am, of chickens in a pool, you can tell that the one in the front is beginning to sink. They can swim, for a while. Then their feathers get waterlogged and they sink and drown.
I put out a wide, shallow pan of water last summer and they finally learned to stand in it or walk through it, but it took a while. Mine run away from a mister or sprinkler, and really, not much water is going to get through all those feathers. My main defense is shade and breeze. It gets over 100F here (37C.) I brought them frozen bottles of water to stand around but they ignored them, too. Ice in drinking water is probably soothing -- they really don't like to drink very warm water, I don't think. I have dunked the hottest looking ones into a bucket of water on occasion; it definitely alters the panting and wing holding-out that they do when hot.
If it's so hot you start thinking about buying them an A/C, you can make a cool place for them by putting a couple of bottles of frozen water into something like a 5 gallon bucket or large ice chest on its side. If they will go in, it's cool in there for a while. Not very practical if you have lots of chickens, though. I also hose bare dirt under a favorite bush so they can dig in it and it stays a little cooler than the dirt that's out in the sun.
