Hillis, 36, remained in intensive care and was "having some problems with his kidneys and his lungs," reported his uncle, Greg Hillis, "but the doctors say he is improving."
The children and adults reportedly were fine.
Members of Escambia County Fire Rescue who responded to the noontime incident at Pensacola Beach on Wednesday, Jan. 4, said the "brave" Hillis "quickly sprang into action to rescue the swimmers in distress" because of rip currents.
They and the lifeguards then rescued him, they said.
A LifeFlight medical chopper flew Hillis to a nearby hospital.
"Even during the colder months, rip currents can still be very dangerous," ECFR wrote in a social media post (see photo at top).
"Rip currents cause more deaths each year than shark attacks do each decade," the department added. They "account for more than 80 percent of water rescues performed by surf rescue lifeguards."
Willis -- who had the distinction of making the cover of the "Madden" video game in 2012 -- had the two children with his now-ex-wife, Amanda.
He played running back for seven years in the NFL after the Denver Broncos drafted him in the seventh round out of the University of Arkansas in 2008.
His greatest success was during his first season with the Cleveland Browns, when he rushed for 1,177 yards. Hillis later had the proverbial cup of coffee with the Chiefs and, finally, played nine games with the Giants before retiring in 2015.
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