What?!?! 3x1000, you're crazy man!! For whatever reason, Masters swimmers despise doing distance work (at least the majority of them) so the longest set we get in a workout is 200's. As part of an Ironman build up, I toss in this 3x1000 workout. It's semi mind numbing, but it's good for your endurance and it's a mental test to see where your mind goes when all you're doing is looking at the black line for 15-20'.
Here's the workout, nothing fancy, but... as the southerners say "that dog will hunt!"
Warm up - 20-30" rest on everything
200 kick - w/fins
3x1000 w/1min rest. All in the 60-70% range building endurance.
- Option to pull round #1 - but that's it, no other gear allowed (not even those awesome Roka shorts)
100 easy swimming - try doing non-free (breaststroke and backstroke ideally to help stretch things out)
100 kick w/board (and fins, duh)