Explorer Ernest Shackleton made his first sea voyage when he was just 16 and was qualified to captain any British ship by the age of 24. He is best known for leading a 27-man expedition to Antarctica aboard the Endurance. Just 400 miles north of their goal, the Endurance became lodged in ice leaving Shackleton and his crew with no choice but to battle the elements to survive. They lived onboard ship and then on the ice for nearly two years before Shackleton led a small group across 800 miles of ferocious seas in a lifeboat to find help. Against all odds, the entire crew survived. Shackleton would attempt the journey again in 1921 and suffer a heart attack on the trip.