Given her lineage and occupation, it’s hardly surprising that environmental activist and filmmaker Alexandra Cousteau is a big fan of recycling.

But it’s more than mildly ironic that for her next expedition—a 14,500-mile, four-month trek through the rivers and lakes of North America—Jacques-Yves Cousteau’s honey-haired, blue-eyed granddaughter is recycling the “Straight Talk Express.” As in: Republican presidential candidate John McCain’s campaign bus—the vehicle for “Drill, baby, drill!” and other environmentally incorrect heresies.

With the defunct McCain logo now painted over in drab purple, the 45-foot biodiesel tour bus is outfitted with Internet access, state-of-the-art editing suites and other multimedia equipment that will accommodate Cousteau’s international production crew of 15; she’ll be leasing it from the same Ohio-based company that McCain did business with.

“I see coral reefs that I used to dive on as a child and are now dead,” Cousteau says. “I see forests that I used to walk in as a child that are now gone.”

“It’s a wonderful bus, and there’s very little we need to do to it, because it has always been used for media,” the 34-year-old Cousteau tells me, sipping a Coke at a sidewalk café in Manhattan’s Meatpacking District. “It’s quite nice. The back windows are tinted for media interviews, and we’ll also be doing lot of outreach from there—Skype video calls with students and schools. The bus has a history now. We’re going to take it in a ‘blue’ direction.”

Cousteau is in town to promote the environmental news site Mother Nature Network (whose board she recently joined) and to celebrate the 40th anniversary of Earth Day by ringing Thursday’s opening bell at the New York Stock Exchange.

She’s still trying to come up with a new handle for her plush ride, but “Blue Legacy” seems as good as any—that’s the name of the nonprofit foundation Cousteau launched in 2008 to throw a spotlight on the planet’s increasingly threatened water resources.

Partly financed by National Geographic, among other corporate and charitable sponsors, Cousteau’s journey, starting from the nation’s capital, will take in water spots in the United States and Canada, including the Great Lakes and the St. Lawrence Seaway, the headwaters of the Colorado River, the Florida Keys, and the Kingston, Tennessee, coal ash sludge spill that, when a dam broke on a containment pool at a coal-fired electricity plant, dumped more than a billion gallons of toxic waste into the surrounding area—100 times more polluting than the Exxon Valdez. Every few days, her team will post a 6- to 9-minute video on the web, and meanwhile produce television documentaries for which she is in negotiations with an unnamed network.

“I’m not an academic; I’m a storyteller,” Cousteau says. “Blue Legacy is a storytelling organization. We’re not out here to get scientists in the field or file lawsuits against polluters or do any of those other really important things. We want to tell the stories about why we’re degrading our water resources and who’s trying to stop it, and how people can get involved and be part of the solution. We need to start understanding the interconnectivity of our water systems if we’re going to be able to mitigate the problems that have increasingly occurred with water scarcity and water quality.”

Water is the central theme of Cousteau’s existence. Born in Los Angeles with dual French and American citizenship, she swam before she walked.

Her late father Philippe (who was killed at age 38 in a seaplane crash near Lisbon) and her mother, Jan, a former fashion model who, as Alexandra says, “traded the catwalk for the Calypso,” put her in the drink at three months old, and started taking her on expeditions a month later. Her famous grandfather—inventor, poet, philosopher, impresario, and hero of the French Resistance—taught her how to scuba dive when she was 7. She has been submerging herself, mermaid-like, ever since.

“Water has always been a huge part of my life,” she says. “I’ve been swimming for as long as I can remember. I feel very comfortable in the water—I find it comforting, familiar, it feels like home. I don’t get to be in the water often enough.”

Cousteau—a Georgetown University graduate who lives in Washington, D.C., in an apartment overlooking the greenery of Rock Creek Park—is mostly dry-docked. “A lot of what I do is advocacy,” she says. “It’s storytelling, it’s speaking, it’s interviews, it’s planning expeditions and fundraising. I’m not only talking about the ocean, I’m talking about freshwater. We all exist in the hydrosphere, all downstream from one another. I’d have to be a marine biologist posted in the field to be diving a lot. I can’t do what I do if I’m in the water all the time.”

Her favorite underwater experiences? “In no particular order, free-diving with humpback whales in Maui; the Galapagos; shark-diving in Rangiroa, French Polynesia; free-diving with spotted dolphins in Bimini, in the Bahamas; I really like the corals in Bonaire in the Caribbean; manta rays in Honduras.”

And yet, Cousteau is worried that human activity and its impact on the environment will eventually cause many of these beloved locales to vanish. ”I see a lot of things that really upset me and are really discouraging,” she says. “I see coral reefs that I used to dive on as a child and are now dead. I see forests that I used to walk in as a child that are now gone. I see tidal pools that I used to play in as a child that are gone. I learned to dive 27 years ago, but I’ve really been noticing these things over the past 10 or 15 years—how much is really disappearing, even in that short period of time.”

She continues: “Increasingly, environmental issues are partisan and political, where it should really be about the quality of life. More simply put, the debate is between those who believe climate change is real and those who don’t. A lot of these issues tend to skew along red and blue lines.”

And what does Cousteau think of the Discovery Channel/TLC's new documentary host, Sarah Palin, a global warming skeptic and, more famously, a former passenger on the Straight Talk Express?

“I don’t have a television set,” Cousteau parries. “I don’t spend a lot of time thinking about Sarah Palin.”

Her grandfather—who died in 1997 at age 87, “was a magical man,” she says. “He was one of the great Renaissance men of his century. He was a war hero, a spy for the Resistance, he was a poet, a filmmaker, he was a philosopher, he played the piano and the accordion. He painted. He loved gadgets. He loved big ideas. He never lost his childlike enthusiasm for life. I remember that when we would walk down the street together he would whistle—just things he made up in his head. He called me ‘ ma cocotte,’ which means ‘my darling’ in French.”

Cousteau says there was never a doubt that she would enter the family business, which, in one form or another, is also the vocation of her brother Philippe and their two cousins. Carrying the Cousteau name “is a huge responsibility,” she says. “It’s not just a continuing legacy, it’s the name my father gave me.”

Philippe Sr., an oceanographer and every bit the explorer and environmentalist that Jacques was, died in 1979 when Alexandra was 3. “They say that the first years of a child’s life, even though you don’t remember most of it, are the most important in terms of being formative. And I have no doubt that being on expedition as a baby and a little girl probably shaped me more than I realized. My father left me an incredible legacy and, more than that, he left me his example and he left me the memory that people have of him. I think that was his greatest gift—and certainly pushes me to ask hard questions and challenge old thinking and try to engage people to re-imagine their world.”

Lloyd Grove is editor at large for The Daily Beast. He is also a frequent contributor to New York magazine and was a contributing editor for Condé Nast Portfolio. He wrote a gossip column for the New York Daily News from 2003 to 2006. Prior to that, he wrote the Reliable Source column for the Washington Post, where he spent 23 years covering politics, the media, and other subjects.