WHAT IT IS: Scaling a 40-foot chain-link fence? No problem. Scaling a 40-foot chain-link fence while horizontal in a water-filled trench with only 10 inches of breathing room? That’s Mudder status. Participants must press their face against the cage and pull their body backward to get to the opening on the opposite side. No one will blame you for taking a Shawshank moment when you reach freedom.