"I'm going to waterski someday...just as soon as I can mentally separate it from being dragged by a boat." --Rita Rudner
Waterskiing is a difficult sport I only tried once. You put on a large pair of skiis and float in the water behind a motorboat while holding onto a long cord. The boat starts to accelerate and you get pulled by a boat through the water. If you position yourself right, you will start to rise out over the water. This is good because once you start getting speed, the water puts tremendous friction on you and the surface becomes hard as you hit it at velocity. If you don't position yourself right, you won't rise and will instead be yanked very hard through the water, which starts slamming you in the face. Seconds into it, if your boatsmen is really trying to floor it quickly, you'll be under a real strain. When I did it, it felt like my arms were going to be dislocated if I continued to hold on, since the water wouldn't let me cut through it so easily. Eventually I had to let go.
Often in college I start to fall behind in the reading assignments. You really don't want to, especially not early in the term. Once you fall behind, you tend to stay behind. Trying to catch up is difficult, and all you can do is keep pace with the lessons but a few behind everyone else. Organic Chemistry seems like everyone's favorite example of this. I wound up taking the class twice, because the first time I got stuck but the class kept moving forward to new material. Hence, it felt like I was being dragged along, but not with my head above the surface. I was waterskiing again, metaphorically speaking.