Warm Up (5–10 Minutes) Start your workout slowly to give your muscles an opportunity to warm up. Focus on your technique: Long strokes move you through the water at a steady pace. Depending on your swimming experience, do a longer swim (400 or 500 yards) or break it up into shorter distances, with rest every few lengths. Start slow and build your pace throughout to raise your heart rate and prepare you to swim harder. Main Set (1600 Yards; 32 Minutes) Use an interval of 2 minutes per 100 yards. For example, the 100 is on 2 minutes, the 200 is on 4 minutes, etc. That means you swim and rest in that allotted time before pushing off to start the next repeat. Adjust as necessary. 1 x 100 Start slow and smooth, transitioning from the warm-up. 1 x 200 Build pace slowly by descending (swim the second half of the 200 slightly faster than the first half). 1 x 300 Hold that pace for the first 200, then descend for the last 100. 1 x 400 Swim the entire 400 at a strong steady pace (the pace you swam the last 100 of the 300). 1 x 300 Keep that 400 pace for the first 200, then build a little more speed on the last 100. 1 x 200 Descend by swimming the first 100 at your 200 pace, then faster for the second half. 1 x 100 Swim this one at your fastest distance pace (not sprinting, but a strong, consistent speed). Cool Down (5 Minutes) Swim an easy 300 yards, broken up into 50s or 100s. Your pace should be the same as it was during warm up. Focus on good technique.