Resources

Backstroke Arm Pull

Ryan Murphy - Underwater Perspective

Take a close look at Ryan Murphy's arm pull technique in slow motion. Notice the way his hand enters the water (pinky first) and leaves the water (thumb first).  

Also, pay attention to how he catches the water with his elbow out and slightly bent (instead of sinking down or locked out to the side) and then pushes with his whole forearm all the way down to his hip.

Underwater Dolphin Kicks

Impossible Underwaters by Michael Phelps

Turns were one of Phelps' specialties - he would often go into a turn neck-and-neck with an opponent, and come up half a body length ahead thanks to his insane underwaters.