Over a decade ago, the U.S. Coast Guard rescued three men in the Gulf of Mexico who had been fishing for grouper when their boat capsized. In order to survive, they had to tread water for 18 hours.

U.S. Marines with 2nd Combat Readiness Regiment, 2nd Marine Logistics Group, practice in-water treading during a water survival advanced course at Marine Corps Base Camp Lejeune, North Carolina, Nov.