SAN DIEGO - UNDATED:  Navy Seal trainees lock arms upon entering the frigid Pacific waters in this undated photo taken in 2000 at the Coronado Naval Amphibious Base in San Diego, California. Hell Week at this beach in San Diego is exactly what it sounds like for third-week Navy trainees who are subjected to nearly unimaginable physical and mental trials. Only the strongest survive the nonstop physical exercise of jogging for miles in deep sand, carrying heavy rubber boats back and forth through the surf, crawling through mud under simulated machine gun fire, and doing myriads of pushups on demand. Hunger, thirst and hallucinations are among the symptoms the men experience, often after only two days. The recruits are divided into teams, and if a team fails to complete a task in the allotted time, all its members must carry "Old Misery," a 350-pound log.  Fewer than half the men survive the week to become Seals, an elite maritime commando force.  (Photo by Joe McNally/Getty Images)