Thirty minutes is enough for a proper session if you don't waste it. Each set below has a short warm-up and cool-down and a main set that fills the middle. The times include rest, worked out at the pace on each card.
Pick the one that matches what you can swim now. If you're quicker than the pace shown you'll finish early; slower and you'll run over a little, so trim the cool-down rather than the warm-up.
4 × 100 free @ 2:00 means swim four 100s, leaving every two minutes; whatever time is left is your rest. 20s rest means rest 20 seconds after each one. Send-offs are set for the pace on each card, so add five seconds if they feel tight. All sets are in metres for a 25m pool. Load this set opens it in the builder, where you can change anything, print it or send it to your Garmin.
For: Regular lap swimmers who can swim 400m comfortably.
If 2:55 is tight, go on 3:05. Same for every send-off on this page.
For: Fitter swimmers who want a hard half hour.
Note your time on the first 100. The aim is to hold it, not beat it.
For: Newer swimmers who can do 100m at a time.
Swim the 100s as 50 free and 50 breaststroke if you need to.
For: Lap swimmers who get bored of straight sets.
Way up is steady, way down gets faster.
It depends on your pace and how much you rest. At 2:00 per 100m, 30 minutes without stopping is 1500m; with a warm-up and rest between reps, expect something like 1200m to 1400m. The newer-swimmer set on this page covers 900m in that time, which is a good session.
Yes, if you have a plan. A warm-up, a main set with a clear job and a cool-down gives you far more than half an hour of drifting up and down.
Add five seconds to each one. The send-offs are written for the pace on the card, and it's better to make every rep than to miss the last few.
All 28 sets are on the workouts page, grouped by goal.