Workout

Warm-up (500)
400 choice
200 drill

Set (600)
4 x 150 on 2:30
...50 kick/100 swim  

Set (2100)
3 rounds
2 x 100 build on 1:30
2 x 50 moderate on :50 
2 x 100 on 1:20
...hold steady pace 
150 on 2:00
...descend 200s by rd
50 easy on 1:20

Cool-down (100)
100 EZ