At BUD/S, running in the sand at the beach is one of the toughest things to get used to, especially if you are working on a running weakness. The student body of each BUD/S class comes from all over the United States, and most do not have the ability to train on the beach like some will. This requires additional running ability (not just average) and plenty of practice with other types of running that make it harder. The good news is that the 4-mile timed runs that are tested each week are on a hard-packed, low-tide beach. However, many of the class runs will be done directly on the soft sand, over dunes, and on very soft dirt roads, which they call the Demo-Pits road. Depending on what phase you are in, you may find rucking on this terrain ever more challenging. It pays to do both in your BUD/S prep running/rucking program.