Near the beginning of the upcoming National Geographic documentary, Sea of Hope: America’s Underwater Treasures , the famed oceanographer Sylvia Earle sits down for a conversation with Dave Palmer, a commercial fisherman. They’re talking about the destructive overfishing of menhaden (sometimes called pogie)–small fish that school in the trillions in the Gulf of Mexico and the Atlantic, filtering the water and providing food for larger species. They’re caught en masse–not to be eaten by humans, but to be ground up into fertilizer or chicken feed. Without them, the ocean ecosystem tips off balance.

“Pogie boats, they go and they take in a whole school,” Palmer says. “There should be limits on all that.”

The 81-year-old Earle, who since the 1950s has spent more than 7,000 hours underwater and witnessed firsthand the devastating effects of overfishing and climate change on the oceans, agrees. “There should be, it seems to me, some places we should just leave alone, like national parks,” she says. “You don’t cut the trees, you don’t shoot the squirrels.”

“They don’t have that now?” Palmer asks.

For the most part, no. In 1983, Ronald Reagan extended America’s sovereign control 200 miles off the country’s coasts, but since then, most of that area, which is larger than the 50 states, has remained open to the taking of wildlife. Sea of Hope, which premiered on January 15, tells the story of how that could change. The documentary follows Earle, the National Geographic photographer Brian Skerry, the activist and writer Max Kennedy, and a team of teenage aquanauts on a year-long voyage around America to persuade President Obama to expand protected areas in the oceans and designate some of its most vital areas as blue landmarks. Traveling from Cashes Ledge in the Atlantic Ocean, to Bucks Island in the Caribbean, to Ewing Bank in the Gulf of Mexico, the team documents the natural beauty and necessity of these locations and builds a compelling case to preserve and protect them.

In one respect, they were successful: Timed to the centennial of the National Park Service in August 2016, the documentary ends with Obama establishing the largest protected area on the planet in the waters around Hawaii. President George W. Bush established Papahanaumokuakea Marine National Monument in 2006, but Obama’s action quadrupled the size of the protected zone. In September 2016, just weeks after expanding Papahanaumokuakea, Obama designated the first marine national monument in the Atlantic Ocean off the coast of New England.

In addition to Papahanaumokuakea, the work of the Blue Centennial initiative found a receptive ear in Obama, who has racked up an impressive array of conservation efforts over the course of his eight-year presidency. Still, Earle says in an interview with Co.Exist, just 2% of ocean area is protected. The Blue Centennial initiative, a partnership between National Geographic, Earth Conservation Corps, and True Blue films, has set a goal of protecting 30% of the ocean in the U.S. Exclusive Economic Zone in an effort to mitigate climate change and curtail harmful human activities like overfishing and toxic waste dumping. Sea of Hope is one aspect of the 10-year initiative, which aims to combine storytelling with advocacy work across nonprofits, technology companies, universities, and all branches of government to further its message.