Long and short passing practice.
Depending on the passingskills you can lengthen or shorten the distance.
Or add the number off passes while the middleman is swimming.
2 passes to 3.
4 swims towards 3.
4 takes the place of 3.
3 passes to 2 and start swimming towards 2.
2 passes to 4 and 4 passes back to 2.
Submitted by: Erwin van Oijen