Sorry, I guess I didn't make that part clear.
I put live shrimps in the chum bag them put them on top of cold packs. There is no water in the chum bag...just regular mesh chum bag. The reason I put them in the chum bag is so they don't flip all over the ice chest and get stuck on the bottom or along the sides when I first put them in. It just makes it easier to manage shrimps in the ice chest. BTW they get real lethargic after the get cooled off.