Just been going through some core swimming principles and that I think you may find handy.
'Hand out of a pocket' concept - When swimming freestyle (frontal crawl), it can be useful to think of the idea of taking your 'hand out of a pocket' after each arm stroke. To assist in remembering the best technique for this.
Backstroke with eyes closed - After mastering the backstroke, you can try to swim backstroke with your eyes closed to perfect it further, as your eyes can mislead you so it'll encourage you to trust your intuitions more while backstroking.
Some physics principles you may want to keep in mind: Newtons Law of Motion and Bernoulli Lift principle,
- Where the former (Newtons Law) is about your arms and legs creating the 'external force' that moves your body through the water (since the Newtons Law of Motion refers to an object remaining in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force).
- While the latter Bernoulli Lift principle refers to an object will always travel from an area of relatively high pressure to an area of relatively low pressure, thereby causing eddy resistance from the space left behind (e.g., after you swing your arms/ kick your feet).
Focus on the basic foundation, i.e., maintaining a good head position and constant kick
"One of the best things a teacher can ever do for a student is to establish a streamlined, high body position...developing a good head position and constant kick - [is] the essence of the desired position...adding arm movements and breathing patterns before this fundamental technique is mastered, may greatly reduce the chances of achieving efficient stroke skills down the track" - Ross Gage, CEO of Swimming Australia