Knock off = Start swimming the distance listed and subtract by amount given each time until you hit the ending distance.
Examples:
200 free knock off 25 each time until at 25 = 200, 175, 150, 125, 100, 75, 50, 25
300 free knock off 25 each time until at 25 = 300, 275, 250, 225, 200, 175, 150, 125, 100, 75, 50, 25
400 free knock off 25 each time until at 25 = 400, 375, 350, 325, 300, 275, 250, 225, 200, 175, 150, 125, 100, 75, 50, 25
BEGINNER WORKOUT:
6×50 easy free on the 1:20 (warm-up)
200 free knock off 25 each time until at 25, RI :15, increase effort throughout until sprinting at end
200 easy swim (cool down)
= 1400
INTERMEDIATE WORKOUT:
8×50 easy free on the 1:10 (warm-up)
300 free knock off 25 each time until at 25, RI :15, increase effort throughout until sprinting at end
200 easy swim (cool down)
= 2550
ADVANCED WORKOUT:
10×50 easy free on the 1:20 (warm-up)
400 free knock off 25 each time until at 25, RI :15, increase effort throughout until sprinting at end
200 easy swim (cool down)
= 4100
My Daily Swim 
Suzanne I am a random person who subscribed to these emails a while back. Since then I have unfortunately not been able to afford a membership to a swim club because of the following reasons… Married, bought a house, had two kids within 2 years of marriage, had to buy my wife a car, as well as our wonderful student loan debt. Anyway, the purpose for this email is to thank you for the many awesome workouts I was able to have through your assistance. Thank you, Tim O’Neill I hope one day to get back into it as well as get my kids into the water
Thank you so much Tim!
Hi, can you explain the knock off with simple explanation ? I still dont understand this
“200 free knock off 25 each time until at 25 = 200, 175, 150, 125, 100, 75, 50, 25”
Does it mean like this :
I go swim 200 meters and then rest for 25 seconds
I go swim 175 meters and then rest for 25 seconds
I go swim 150 meters and then rest for 25 seconds
…..
I go swim 25 meters and then rest for 25 seconds
You’ve got it except rest 15 seconds (instead of 25).
Did the intermediate set today. Great workout.