Not only is this project inexpensive, but it’s safe to use with kids (and even pets) and works unbelievably well. The secret? Polymer beads. This product is the magic that is used in most disposable diapers (but you can find yours in the floral department) – so it’s very absorbent and stays that way for quite some time. That means that when soaked in cold water they retain the chill for several hours. Best of all, these can be made in under an hour – so everyone can have one before your next adventure.