Think of it as "how to get a group across a potentially tricky/flooded stream." The strongest swimmer crosses first, tied to the rope. Everyone else crosses the rope (hand over hand under the rope with your legs crossed over works if you don't have a "seat," but a carabiner-powered zipline would be more fun). Then the last person in the group unties the rope, ties it around his or her waist, and gets pulled across. They (as of ~15 years ago... jesus I've grown old) practice this in ROTC.