20' run with 6x30" strides. These are best if done on a slight downhill on a dirt path. Warm up for at least 10' before the first stride. For your recovery, you can walk back to the starting point. Strides are quick bursts that are as fast as 5k pace. You are looking to get in about 45 left foot strikes per 26-28". Stretch when done and add in Core 1, 2 or 3.
Swim 4 laps (8 lengths), and take a 1 minute break. Do this 7 more times for a total of 1600 yards.