Once you have traveled to the dock, you throw out lines to tie yourself to the pier. As the water rises and lowers, the ship goes with the water. Meanwhile, the pier stays still and the lines tighten or loosen as the height difference between the ship and the pier changes. Frequently, the height change is slow and small enough so that those on watch can adjust the lines. On the mighty Thames, the tidal range is over seventeen feet.
Tidal range is the difference between high and low tide.
Instead of tending lines, the English build floating docks. Another item the cadets experienced was interaction. Interaction is a phenomenon that happens when ships pass each other in shallow areas. A ship acts as a wedge in the water. The bow cuts through the water and puts pressure on things forward of the vessel, pushing forward and away.