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.
Great Britain pulled off a surprise comeback , with Duncan Scott clocking the second-fastest 100 Free split in history.
Pay special attention to the relay starts: the arm swing and step helps swimmers gain momentum before going into the water (this is not allowed for regular starts).
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.