Bob underneath rows of floating barrels as you battle the freezing water temperatures. This obstacle requires mental grit, as extreme cold can be as challenging mentally as it is physically. Focus on breathing, and move quickly through the water to complete the Underwater Tunnels and warm up once you are ashore. You can prepare for this obstacle by swimming in ice-cold bodies of water, or taking cold showers. Try to regulate your breathing and control your heart rate in order to acclimate your body to cold water conditions.