As I give a waterski lesson, one of my primary focuses is on a skier's body position. There's lots of different styles of slalom pulling positions, but whatever it looks like you have to have a strong, leveraged pulling position to get across the course effectively.
One way to increase your leverage, and therefore increase your ability to get across the course on an earlier line, is by counter-rotating. Counter-rotating means opening up your body so that your hips and shoulders are facing more down the length of the course as your ski is pointed across the course. For example, say you're turning and cutting to the right. As your ski is arcing around to the right you're trying to make your shoulders and hips twist a bit to the left. With a good, countered body position the observer in the boat should be able to see the fronts of both of the skier's shoulders.
What countering allows you to do is soften your legs better, and get your hips or center of gravity leaning away more from the boat. This will shift your body's weight so that you have more pressure over the ski's cutting edge, and make it possible for you to hold a better line cutting more directly across the course. This will set you up for wider, earlier turns. If you close off your hips and shoulders, making them face across rather than down the course, your legs will tend to be straighter and stiffer and your hips or body's weight will be placed more over the center of the ski. This will lessen your ability to hold your ski on a solid edge, which leads to shallower, faster approaches to your turns.
Written by Terry Winter