Naval Amphibious Base Coronado, California, Aug. 13, 2010: Sunburned Navy SEAL candidates stand at attention on the beach, preparing to grab small zodiac boats and enter the sea.

Hell Week — which happens in the third week of the Basic Underwater Demolition/SEAL (BUD/S) training - is the five-and-a-half day of cold, wet, brutally difficult operational training on fewer than four hours of sleep. On average, only 25% of SEAL candidates make it through Hell Week.

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