At the 58 minute mark.

In the scene at the gym when Hal and Mauricio are talking about Rosemary's "cankles",

notice that Hal picks up the towel and just holds it his hand.

In the next shot, the towel is on his neck.

Then the shot changes while Hal says that "Rosemary doesn't have 'em" and in that shot the towel is off again.

He's apparently REALLY fast with his hands.