The Endurance Course: What You Need to Know. The Endurance Course is a 2.5 mile obstacle course through the beautiful woods of Quantico. And passing it in a time limit is a mandatory requirement for completing OCS.
First, candidates run the Obstacle Course (O-Course) in boots and utes (just wearing boots and trousers)
While you run the course, it is not sprinting but a steady run with a ten pound rifle and maybe 20 pounds at most of gear, in boots. I highly recommend buying boots and slowly increasing intensity and distance in running in boots. Run on trails, on hilly terrain if preferable. I do NOT recommend running through water, as the friction is almost guaranteed to give you painful blisters that will impede your training.