An island nation in the Pacific Ocean that's smaller than New York City has created an ocean reserve that's bigger than California.

The president of Palau signed legislation Wednesday designating a reserve that's about 193,000 square miles (500,000 square kilometers) in size. This makes it one of the five largest fully protected marine areas in the world. (Read about Chile's newest marine reserve.)

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President Tommy Remengesau Jr. signed the designation and retweeted accounts of the ceremony and notes of congratulations.

Palau's Congress had recently signed off on keeping 80 percent of its territorial waters from any extractive activities, including fishing and mining. The remaining 20 percent would remain open to fishing by locals and a limited number of small commercial operations.

"Island communities have been among the hardest hit by the threats facing the ocean," Remengesau said in an earlier statement. "Creating this sanctuary is a bold move that the people of Palau recognize as essential to our survival."

Enric Sala, a National Geographic Society explorer-in-residence and head of the Pristine Seas project, said that "Palau has really blown it out of the water."

The country "is one of the places with the highest marine biodiversity on the planet," he says. Pristine Seas helped evaluate the effectiveness of smaller, traditional marine reserves in Palau.

The country's waters are home to over 1,300 species of fish, about 700 species of hard and soft corals, and marine lakes that host hordes of non-stinging jellyfish.

Experience the the stunning biodiversity of the Republic of Palau's waters with National Geographic’s Pristine Seas.

Palauans have a long history of bul, or setting aside smaller reef areas during fish spawning and feeding periods as a way of giving those populations time to recover from fishing practices. The federal government has now effectively extended that practice to encompass the majority of the country's ocean.

The government is still working out the details when it comes to enforcement of their new marine reserve. The nation has no military and only one law enforcement ship.

But "Palau is serious about enforcing their laws and protecting their resources," says Sala. Earlier this year, the country confiscated wooden boats from Vietnam that were fishing in Palau's waters illegally and burned them. (Learn more about the incident.)

"We will not tolerate any more unsustainable acts," Remengesau told National Geographic earlier this year. "Palau guarantees, [poachers] will return with nothing."