This broken endurance set keeps the mind engaged with a different focus for each interval.
10 min easy
Follow this pattern (except the 4×25 at the end): First swim is cruise, second swim is race pace (your next “A” race), third swim is easy at the walls and sprint between the flags, fourth swim is a build to 90%.
600 as 4×150 500 as 4×125 400 as 4×100 300 as 4×75 200 as 4×50 100 as 4×25
Note: These are all sprints—take long rest as needed. Not the same pattern as the rest of the set.
2–4 x 200 pull with paddles optional as time allows