Hall's cousin is Chief petty officer Charles Keating IV, a Navy SEAL, who was killed at age 31 in combat with ISIS in Iraq in 2016.

In his first Olympics at the age of 21 in Atlanta, Hall had only 6 years of swimming experience yet he already had a well-known rivalry with Russia's Alexander Popov.

Prior to the 4 × 100 m freestyle relay, Hall posted on his blog: "My biased opinion says that we will smash them (Australia's 4 × 100 m team) like guitars.

But the logic in that remote area of my brain says it won't be so easy for the United States to dominate the waters this time."

[4] The Australian team responded to Hall's remarks after the race by playing air guitar on the pool deck.

"[5] Another member of Australia's victorious 4 × 100 team, Michael Klim, recalled that "Hall was the first swimmer to come over and congratulate us.

The decisive moment in the relay race had been Klim's opening leg where he set a new 100-meter world record of 48.18, gaining a 0.71-second advantage over Anthony Ervin, a lead which his Australian teammates successfully defended.

The robe even earned Hall a fine during the 2004 Olympics, as the Everlast-made apparel violated the uniform supply agreement the team had with Speedo.

[11] His eccentricity has won him a great deal of fans, but what some perceive to be "showboating" has drawn substantial criticism.

He is also an outspoken critic of performance-enhancing drug use in swimming, and is one of the few prominent swimmers willing to publicly question the legitimacy of suspected individual accomplishments.

In 2008, he compared International Swimming Hall of Fame inductee Amy Van Dyken to disgraced track & field athlete Marion Jones, noting they were both clients of the Bay Area Laboratory Co-Operative (BALCO).