Run on a flat path, track or treadmill. You can use the 8/2 method of 8 minutes running, 2 minutes walking. While running, run like a Kenyan - smooth and efficient. RPE should be light - 5/6 out of 10.
WU: 200 yds
MS: The next set will be 8 x 50 on 30" rest. This means 50 yards sprint, 8x, each time with 30 seconds rest when you finish. Then swim 200 yards of drills (mix it up) and then swim 4x 25 yards fast with 15" rest.
CD: 100 yards easy