[sunstone]

The problem with this is that the current is constant. When doing a long set I sometimes accent the arms and the legs alternately over say 200m. Well typically three lengths of arms and one length of kick dominated effort. The thing is the speed does change from one technique to other but moving the water at a constant speed over a short distance doesn't work properly. So it's cute for a little swimming but it's not compelling for serious training. Never mind if you want try doing an individual medley set.

[Super_Jambo]

make it a bit longer and have it vary the speed on the position of the swimmer...

[Retric]

Or just have the water channel narrow so the water velocity increases as you move forward.