Descending 100s on the Pace Clock

About 2,000 m, 45 to 50 minutes. Teaches the skill most fitness swimmers lack: changing gear on purpose. Warm-up: 300 easy, then 4 x 25 build. Main: 3 rounds of 4 x 100 on a fixed interval, each 100 faster than the one before. Swim 100 easy between rounds. Cool-down: 200 easy. Pick an interval that leaves about 20 s rest on the first 100 of each round, for example 2:00 if you swim an easy 100 in 1:40. The first repeat should feel almost lazy and the fourth close to your best, which is harder to judge than it sounds. For a shorter slot, drop to two rounds and 1,500 m.