Ours CANT swim... I have had a couple drown in the horse tank... sickbyc (thats a gross thing to clean up!) They will drown in anything they can't step up out of. They can't get over the side of a stock tank. That's why I was testing it with bricks to make sure they could get out. Any container of water deep enough they can't touch or too narrow they can't spread their wings (buckets) they can drown in. Always put a way out in any container of water too deep for chickens to touch the bottom.