Workout

Warm up (600)
400 swim
200 kick

Set (600)
6 x 50
2 on :50, 2 on :45, 2 on :40, 2 on :35
4 x 75 on 1:15 
...kick/drill/swim by 25, 

Set (400)
4 x 25 variable on :30
   #1: hard/easy
   #2: easy/hard
   #3: all easy
   #4: all hard
100 kick
2 x 100 on 1:30
…descend 1-3

Set (1200)
4 rounds
4 x 25 ez on :30
100 (75% catch-up drill)
2 x 50 sprint on 1:00

Cool-down (200)
200 EZ choice