I do this method often on backcountry trips. Both for meat, but also when I pack in frozen brats/burgers for some backcountry hunts....works like a refrigerator. I keep 3-4 contractor bags in my pack, as I also like to use one for storing the meat/game bags on to keep them clean when I'm gutless deboning the animal.
If I don't have a natural water area deep enough to fit enough of the bag in then I build a small damn. I like to use cord to tie the neck to a nearby tree or rock to help keep the bag upright. I usually double up the contractor bags to make extra certain it's waterproof. Personally I try to get it in a creek that is cold enough water, instead of a lake, if I can. Keep in the shade, as the black plastic attracts heat if in the sun.
If using this method, I like to air dry the meat a bit before putting in the bags. And I usually take the meat out and check it and sometimes re-air dry it for a bit if I'm staying in on a longer trip to help others fill their tag.