Workout

Warm Up (500)
10 x 50 
...choice swim

Set (600)
6 rounds
4 x 25 on :35
…odd rounds fly/even rounds choice
kick/drill/kick/full stroke

Set (900)
12 x 75
…odds free/choice/free on 1:15
…evens all free on 1:00

Set (1200)
6 rounds
100 on 1:30
4 x 25 on :30
…odd rounds 25s alt fly/free
…even rounds 25s alt choice/free

Cool-down (200)
200 choice