How to Improve Your Swim Skills

I'm working with a guy at the moment on his on his swim and one of the things he does is he's very shallow through his catch. I told him to do 20 50s with 20 seconds in between just keep it 60% and I want you to count your strokes for each 50. The one that gives you the lowest stroke count provided you push off the same will likely be the best change. You know how are they supposed to know if they're doing the right thing unless they have that ability to keep bouncing off you? It's got to be the future of progression surely.