This Video will concentrate on Part 2 Thumb Hits the Thigh.
This will continue to teach and develop the importance of underwater pulling and allowing the arms to pull 100% water without any interference of air bubbles and rushing the arms which take away from the efficiency.
Don't move onto Part 3 until this part 2 is mastered,
Each part has a reason behind it. Take your time and allow the stroke to develop with repetition.