It was Argentina's third title but Martinez is the first World Cup winner from the resort town south of Buenos Aires, where tennis player Guillermo Vilas was previously the most famous sports personality.
Martinez showed the crowd in front of the beach on Thursday his trophy as goalkeeper of the tournament and told them it was "not only for me but for all the kids, the little goalkeepers, who dream of going for the fourth star."
"This is a beautiful thing, that a goalkeeper gets this recognition, because this is almost always given to strikers," said Martinez, who left Argentina at 17 to join Arsenal in England and now plays for Aston Villa in the Premier League.
He has developed a reputation as a penalty shootout specialist after his success in the 2021 Copa America final against Brazil and then against France in Doha.
"On penalties I become strong and I know that people respect me, I know because opposing players have told me so," he said.
Martinez defended his strategy of trying to disconcert penalty takers.
"When you take the first penalty in a world final, you know the other guy is going to be very nervous," he said. "I try to play them, to push the ball away a little bit, to talk to them."
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