Kjell & Terry,
Thanks for another wonderful thread! Kjell, my first experience with swimming a set the "TI Way" was at my coach training a year and a half ago.
Terry had us swim (in a 50m pool), 50m, 100m and 150m counting strokes. I beleive I started with around 37 stokes @ 50, then 37/38, and finally 39/42/43. Frankly I was also terrified as I'd never swum in a 50 m pool, nor a pool that was that deep (although I've swum alactraz adn loved it).
The next 30 seconds that followed in which Terry asked me what my counts were life changing. Suddenly lightbulbs and a whole new understanding came over me. terry has already mentioned the various metrics that can be manipulated to create any aspect of swimming improvement that you'd like
In my case, I could have create sets of 50s & 100s aiming for a stroke count of 37 to improve my imprinting of that stroke, and as a consequence, the ability to hold that effort for longer (as well as holding technique). But what really stood out was that I could also choose to simply rest LONGER prior to trying the 150m with the aim of keeping my stroke counts at 37/38.
It seems like you already understand this basic idea, but be aware that the variety of ways to implement it are limited only by your imagination.
I come to the forums often to dip into the number of ideas that Terry & others have shared here the post and as he's done above.
Building speed is done in the same way. One needs to either increase rate or decrease strokes in order to get faster. Once a test set has been done (like I mentioned above), "training" sets can be designed with specific goals in mind that will be unique to each swimmer in the group...yet all can share in the same workout, or practice as we like to refer to them.