(-) = Negative split, where the second half of the distance is swum faster than the first (e.g. (-) 100m)
"Descending" and "ascending" refer to swimming increasingly fast through a set (descending) or starting fast and then getting slower through a set (ascending).
There are quite a few swim drills, as well, including sculling (Sc), fist, head up (h-up), drag finger tips (dft) and one arm. These drills work mainly on "feel" for the catch and pull phases of the stroke.
Deciphering the Workout
After you've learned the basics, the next step is learning to read a swim set. Swim set descriptions are usually fairly clear. Sometimes, however, as in the world of academics, where it often seems the professor is either trying to confuse his or her students more or just impress them with his grasp of the English language, the swim coach can get carried away as well.
The bottom line is that we are just describing a workout. Sure, it can be creative, but it should make sense and be simple enough for people to remember.
For example:
2x (4x50m FR 1-4 on :45 / :55 / 50 choice ez :15 RI )
OR
2x 4x50FR 1-4 on :45 / :55
50 ez :15 RI
These two sets are identical and show that there are a few ways to write the same thing. This set reads as two sets of 4x50m with 50m swim choice in between. There will always be a few monster sets with brackets within brackets, and then you will have to rely on your old college math and physics classes to help you make sense of them.
I also threw in a send-off time. That's the part that reads "on :45 and :55", which means that if the 50m took you 38 seconds, you then have seven seconds of rest left before you have to go again in the case of the 45-second send-off and 17 seconds of rest if you go on the 55-second send-off. For 100m sets you will have send-offs of 1:15, 1:20, 1:30, and so on.
The entire swim workout is comprised of sets. Usually the coach will start everyone off with a warm-up, and then maybe a little drill set followed by perhaps another little pre-set with some descending 50's to get the swimmers ready for the main set. After the main set, it is pretty common to go right into the cool-down, but you never know what kind of mood your coach will be in. You may find yourself having a kick set thrown your way before it is all over.
I hope this little lesson helped you make some sense of what is on the dry erase board and ultimately avoid any possible personal embarrassment.