Ultramarathon runners run in races of 50 miles or more! These athletes have to be very careful to drink enough water. If they don't, the inside of their bladder can get so dried out that the sides rub together until it's scraped, raw, and bloody. The runners know this has happened when their pee turns dark red. Not a good sign!
Runner #3 has two water bottles strapped to his hands. Can you find 12 others?