Mallett, 35, was identified as the tourist who was not breathing when lifeguards pulled him out of the water on the beach in Destin, Florida, on Tuesday.
The Okaloosa County Sheriff's Office said he had been with a group of people who were struggling to make their way back to shore. Officials initially said a man went under and lifeguards reported that he was not breathing when he was pulled out.
"Lifesaving measures were immediately undertaken but the man was pronounced deceased at the Destin Emergency Room," the sheriff's office wrote in a news release.
Deputies later were able to identify the swimmer as Mallett of Arkansas.
"We send out heartfelt sympathies to his family, friends, and loves ones in his tragic passing," the sheriff's office said.
Tributes poured in after initial reports about the death.
The NFL passed on its thoughts to the University of Arkansas alum's friends and family.
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"The NFL family is deeply saddened by the passing of Ryan Mallett. Our thoughts are with his family and loved ones," the NFL posted on social media.
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Mallett's former Texans teammate, JJ Watt, offered his own remembrance to the QB.
"Horrible news to read about Ryan Mallett. Gone way too soon. Rest in Peace brother," Watt tweeted.
A former 2011 third-round pick of the New England Patriots, Mallett played with the Texans for two seasons in 2014 and 2015, starting a half dozen games before he missed a team flight to a road game.
Mallett also spent time with the Baltimore Ravens from 2015 to 2017 before retiring from the league.
Recently, Mallett was a head coach at a high school in Arkansas.