Workout

Warm-up (700)
400, 200, 100 on 1:30 base
...last 50 of each repeat = stroke

Set (600)
Kick-swim 2 rounds
200 kick/100 swim on 4:00
...kick is FAST, swim is cruise

Set (2,000)
400, 400, 300, 300, 200, 200, 100, 100 on 1:20 base
...1st repeat in each section is aerobic
...2nd repeat is "as you feel", but faster than 1st 
...those going strokes adjust distance

Cool-down (200)
Swim 200 moderate to EZ