This is a simple set designed to help your swimmers physically explore the relationship between stroke tempo, stroke length, and speed.
8 x 25 @ :35 all one stroke, choice
odds minimum cycle count (long strokes)
evens maximum speed (count cycles for comparison to odd 25s)
1 x 200 @ :20 rest
Steady swim of the same stroke as the 25s, try to hold a cycle at or within 1 cycle of the minimum count from the odd 25s. This should be challenging, particularly if the pace is pushed a bit.
Repeat as many times as you want!