Some hydration packs are insulated to keep water from freezing or becoming warm.

Some competitors may choose to carry food or water on course, and wear a small waist pack or hydration pack for this purpose.

It has a built-in hydration pack, basically a plastic bladder with a hose coming out of it.

"Small is big," Mr. Gallagher said, noting that hydration packs, which hold water and little else, are top sellers.

"Got it," I yell back to Tara, who is at my side already, siphoning some water off my hydration pack.

Not to be confused with the hydration pack, dromedary bags are able to carry larger amounts of water.

Most hands-free waist-mounted hydration packs also offer storage for keys or energy gels.

In that case, you might want to strap on a hydration pack, which is basically a backpack that holds lots of water.

Water may be stored in bottles or in soft, collapsible hydration packs (bladders).

In addition, Marines can wear a watch cap and gloves in cold weather, or a hydration pack to prevent dehydration.