BOSTON - Confetti rained down and the “Hallelujah Chorus” resounded through city streets Saturday as grateful fans embraced the World Series champion Boston Red Sox, hailing the team as heroes during a jubilant parade that even went afloat on the Charles River.

An estimated 3.2 million fans packed the seven-mile parade route in spitting rain and temperatures in the 50s, standing in dense crowds, hanging from windows and cheering from rooftops.

Some held signs bearing words of thanks, marriage proposals and expressions of wonder at the team’s achievement after 86 years of dashed hopes since its last championship in 1918.

“All is forgiven,” read one banner. “Now we just have to wait for the other six signs of the apocalypse,” said another. And dozens said simply: “Thank you.”

“It started raining and it was cold and the people didn’t even care,” pitcher Derek Lowe said. “They’ve waited a long time. You’ll never see a parade like that with so many people, no matter what sport or what city.”

The parade wound from Fenway Park, past Boston Common and City Hall and onto the Charles River, with Red Sox players riding 17 of the amphibious vehicles known since World War II as “ducks.”

Chitose Suzuki / AP Red Sox pitchers Pedro Martinez, left, Curt Schiling, center, Derek Lowe, right, wave to spectators from the Duck boat on the Charles River in Cambridge, Mass.

Businesses along the route rose to the occasion, with one wedding boutique putting a bright red “B” on each dress in its display window. The Loew’s Theatres at the Boston Common used huge letters to change its name to honor Lowe, who won the clinching game in each of the team’s three postseason series.

Throughout the parade, music blared from speakers on the lead vehicle, with selections including the “Hallelujah Chorus” from Handel’s “Messiah,” and “Dirty Water” — the Boston-themed Standells hit that is played after every home victory at Fenway Park.

The players were awed by the outpouring of pent-up emotion from generations of fans. It even dwarfed the party thrown for the Super Bowl champion New England Patriots earlier this year.

“I couldn’t believe how loud it was,” catcher Doug Mirabelli said. “It’s just something you never get tired of. I just wanted to keep going.”

Right fielder Trot Nixon said the World Series victory was for those “who have lived and breathed with Red Sox baseball for years and years.”

Pitcher Pedro Martinez was hit in the forehead by a baseball thrown from the banks of the Charles. He looked stunned and put his hand to his forehead as the ball floated down the river.

“I have a little headache, but I’m OK,” Martinez said after the parade.

Nixon said he heard heartfelt words from fans, like one who said his grandfather had died before seeing his beloved Sox win the big one.

“Well, he’s got the best seat in the house now, up there with our Maker,” Nixon said. “This is for all the little guys, from Maine to the West Coast. All the fans are part of our family, the family of the Red Sox.”

Charles Krupa / AP Fans surround vehicles carrying members of the Red Sox during Saturday's parade through the streets of Boston.

Police reported that 15 people were arrested, 12 people were brought to the hospital with minor injuries and 30 people received medical treatment in the street. Those arrested faced charges including disorderly conduct, drug possession, public drinking and assault.

At an impromptu mini-rally at Fenway before the parade, manager Terry Francona said his team always had what it took to win even if his scruffy players — who dubbed themselves “idiots” — didn’t always look serious.

“They may not wear their hair normal, they may not dress normal, but they play the game as good as you can,” Francona said.

During the parade, several players hoisted signs that said “Idiots Rule!”