Mystic — A crowd of people at the Mystic Seaport Museum watched in anticipation while the Mayflower II was slowly lowered into the Mystic River on Saturday as the United States Coast Guard Band played.

"The Mayflower II is afloat!" shouted Quentin Snediker, shipyard director and senior curator for watercraft, to loud applause from the audience in the seaport's Henry B. duPont Preservation Shipyard and the sounding of horns.

Mayflower II's official relaunch marks a milestone in the ship's multiyear restoration between the Mystic Seaport Museum and Plimoth Plantation. Speakers during Saturday's ceremony remarked on the importance of the work and thanked all those who had a hand in preserving the replica of the ship on which the Pilgrims made their journey to the New World in 1620.

"Mayflower II is truly a national treasure," said master of ceremonies Jared Bowen, WGBH Boston's executive arts editor. "Because of this restoration, she’ll be able to sail far into the future and carry on her educational mission for generations to come."

During the ceremony, Harriet Cross, British consul general to New England, christened the ship with water from England, the Netherlands and all 50 states.

Capt. Whit Perry, Plimoth Plantation's director of maritime preservation and operations, said the future of the Mayflower is assured for at least another 60 years and the next 25 million or so people who will step aboard.

Mystic Seaport Museum President Steve White called renewing an aging vessel "a marvelous act" and said the shipyard now is adding the Mayflower II to its list of preservation projects, which also includes the 19th century whaling ship Charles W. Morgan.

Steve Brodeur, chairman of Plimoth Plantation’s board of trustees, said the ship gets the honor of returning to the water "because of the hard work and the dedication of so many of you here who have cared about this ship, her amazing story and her place in history."

On May 14, the Mayflower II is slated to arrive in Boston, where it will be escorted into Boston Harbor by the USS Constitution to kick off a six-day maritime festival at the Charlestown Navy Yard commemorating the 400th anniversary of Mayflower’s Atlantic crossing, Brodeur said. The ship will return to Plymouth, Mass., the following week and then sail in September to Provincetown to commemorate the signing of the Mayflower Compact.

Ellie Donovan, executive director of Plimoth Plantation, said the Mayflower is "the once-upon-a-time to the story of how this land became the United States."

"This beautifully restored sailing ship matters because she helps tell that complex story and because she speaks to something in all of us," she added.

The Mayflower II, which was launched from England and reached Plymouth in June 1957, was given by England to the United States "to honor the bonds of friendship formed during World War II," The Day reported.

Nathaniel Philbrick, the author of the 2006 history book "Mayflower," gave a keynote address that reflected on both the journey of the Mayflower in 1620 and the journey of the Mayflower II in the 1950s. He said the Mayflower II is more than just a replica, but a famous ship in its own right.

"She is also a symbol, a source of inspiration to those in search of new beginnings and the possibility of multicultural cooperation in this nation of immigrants," he said. "She also speaks to the dark truths underlying the settlement of New England and America. Upon her return to Plymouth Harbor, she will once again become a kind of time machine, a fascinating floating theater upon which some of the most passionate historians I have ever had the pleasure to know transport the visitors to Plimoth Plantation to a past that only gains in resonance and importance with each passing day."

Kerri Helme, a member of Mashpee Wampanoag Tribal Nation and guest experience and cultural programs manager at Plimoth Plantation, and The Rev. Anne Robertson, executive director of the Massachusetts Bible Society, delivered the invocation. The ceremony featured musical performances by Justin Gigliello and Gilly Assunção.

Virginia Ricketts of Bozrah attended the ceremony with her daughter Sarah Baldi of Waterford and Sarah's husband, Jonathan, and their 7-year-old daughter, Lena, and her friend.

Ricketts' sister had traced the family's genealogy and found their ancestors had come over on the Mayflower. The family gathered for a reunion in Plymouth, Mass., this summer and planned to return there, where Ricketts' daughter Christine lives, to see the ship's return.

Sarah Baldi said she enjoyed meeting other descendants of the Mayflower at the event, and Ricketts said that hearing the speeches, she could visualize actually being on the ship.

"It was amazing," she said. "It really was."

Ricketts said her family talks about the importance of history, and the event is "history in the making." Her granddaughter will now be able to say she was there when they restored the ship and got to see it launched.

Nearly 3,000 people visited the seaport on Saturday, which Dan McFadden, the museum's director of communications, called a "great day of attendance."

k.drelich@theday.com