Workout

Warm-up (200)
200 swim

Set (1200)
8 x 150's on 2:30
...50 free/50 kick/50 free

Set (2000)
400 swim on 6:00
2 x 200's on 2:40
...negative split  
4 x 100's on 1:20
...hold solid pace
2 x 200's on 2:40
...negative split
400 swim on 6:00
...descend 1-2 on 400's

Cool-down (200)
200 EZ