Here’s a look at the BUD/S obstacle course as run through by an actual SEAL with a helmet cam.
In training a class will line up by their last recorded time and adjust in rank according to how fast or slow they are. Imagine two hundred guys staggered, it gets jammed up real quick with guys clawing over each other for a faster time. The good news is that in BUD/S the class size gets small really fast so the obstacle course gets less crammed up.
We would typically bury the slowest guy (by instruction) at the finish line so he could watch everyone run over him, only his head was showing. You did NOT want to be “that guy”…