You can do this as a dolphin, flutter, or breaststroke kick set. The set, as written, uses a 30-second sendoff base per 25, but you can adjust this up or down. The idea is to get approximately 10 seconds rest after each kick segment and a bit more rest after each swim segment.
If you have a Tempo Trainer, this is a great set for using it, because it will help you maintain a consistent level of effort. Set it at a moderately fast setting for the 100s. Increase the cadence by .05 or .10 on the 75s, and by another .05 or .10 on the 50s. Here’s the set:
9 X 100 on 2:00 sendoff, alternate 2 X 100 kick/1 X 100 swim
100 easy recovery
9 X 75 on 1:30 sendoff, alternate 2 X 75 kick/1 X 75 swim
125 easy recovery
9 X 50 on 1:00 sendoff, alternate 2 X 50 kick/1 X 50 swim