Workout

Warm-up (600)
3 x 200 
...50 drill/100 kick/50 swim 
...choice 
…rest 20-30 

Set-1 (400)
8 x 50's on 1:00 
...choice stroke 

Set-2 (1600)
4 x 400 on 7:00/8:00 
odd - 200's free - build to solid pace 
even - 200's IM - descend 1-2  

Set-3 (400)
4 x 100 choice kick on 2:30 
…descend 1-2 

Warm-down (400)
400 moderate to EZ 
…choice