FAIRCHILD AIR FORCE BASE, WA, UNITED STATES

S-V-80-A combat survival students gather water from a stream June 13, 2015, in the Colville National Forest, Wash. To prevent water-borne illness from occurring, the students learned to add iodine tablets or bleach to purify the gathered water. The students also learned that leaving a bottle of water in the sun will result in water purification by the sun’s ultraviolet rays.

Courtesy of DVIDS