Workout

Warm-up (600)
400 swim
...every 3rd 50 back
200 kick

Set (600)
12 x 50 build on :55
…4 cb

Set (1900)
4 x 200 on 3:15 
…build by 50
4 x 150 on 2:30
4 x 100 on 1:30 
…descend 1-2
2 x 50 on 1:30 
…FAST!

Cool-down (200)
200 easy