Braxton Bilbrey, a 7 year-old Arizona boy, swam from Alcatraz Island the site of the infamous former maximum security prison to the city in 47 minutes thus creating the record for the youngest ever to swim in the chilly waters.

The young champ was joined by his coach and two other adults for the estimated 2,25km swim on Monday and was greeted at the finish by reporters, photographers and well-wishers.

Braxton said his next ambition is to swim the 33,8-kilometre-wide English Channel. He said he ate pizza for dinner Sunday and was helped along by shouts of encouragement from his coach, Joe Zemaitis.

The toughest part of the swim was the water temperature, the boy told the Associated Press.

San Francisco Bay is known for strong currents and rough waters.

Alcatraz, once home to a notorious federal prison that housed some of the nation's infamous criminals, including Chicago mobster Al Capone, is now a tourist site that attracts about one million visitors a year.

The second- grader, who lives in Glendale, Arizona, got the idea when he saw a magazine story about a nine-year-old boy who made the swim.