Easiest way to improve your swimming using video GoPro or (smartphone) of yourself

Easiest way to improve your swimming using  video GoPro or (smartphone) of yourself
One of the best ideas I had when I began my swim training and improving my freestyle, was recording video of my swims during my pool sessions. This was an indispensable training tool, since it allowed me to see from a third person view what I was doing, it is the fastest way to improve ...