Cocos is a young island, formed roughly 400 million years ago. It's very mountainous, rising from sea level to its highest peak, Cerro Iglesias, at more than 2,000 feet (610 meters).

The island gets 20 to 30 feet (6 to 9 meters) of rain a year, and after it rains, the island's waterfalls are a spectacular sight. Getting to shore is no easy task, however: boulders the size of cars ring the island. But once you're there, it's like another world, and another time.

"There are few places in the world that have what Cocos has to offer," says diver Peter Tattersfield. "The lush greenery, the surroundings, the waterfalls, and the fauna and the marine life below the ocean, below the waves, make it something worth preserving. ... It feels like you've stepped back 50-60,000 years when you arrive... and I bet you it hasn't changed much from that period of time."

Begin a walk to the waterfalls for a sense of just how solitary the island really is. Roosevelt palm trees -- named after frequent visitor U.S. President Franklin D. Roosevelt -- give way to the jungle, where hiking is a definite workout.

"The climbs are not easy, if you actually climb near the top of the mountain," says visitor Mike Tattersfield. "So if you're a nature lover, it's great. The birds are beautiful, especially the spirit de santos, the white dove-type bird."

Cocos Island is considered a natural laboratory to witness the evolution of species. Visitors can see a nesting area for the islands' 80 species of birds -- three of which are found only on Cocos -- or walk on the trails and try to catch a glimpse of the lizards, some making their homes in the Cocos Island coffee tree.

One species that isn't native to Cocos -- and is causing some difficulties -- is the pig. Brought to the island during attempts at settlement 100 years ago, these animals run wild, uprooting vegetation and causing soil erosion.

The government of Costa Rica recognizes the uniqueness of Cocos Island and is determined to put limits on development and tourism.

"We are looking for quality tourism, not quantity, for a tourist that comes, respects our national parks and our ecosystem," says Costa Rican President Jose Maria Fugueres.

Avi Kalpfer, owner of one of the live-aboard boats that makes the long journey between Cocos and Costa Rica, says he hopes the island never changes.

"In (the) case that it will (be)come populated like other places, I believe that personally, myself, I will have to leave again," he says.

Visitor Larry Serafin says the island is "one of the last remaining jewels." The rangers who guard the island, he says, "work their tail off for almost nothing."

"They spend their days out there, living in a shack, making sure that fishermen don't come in here and strip this natural wonder of something that your children and your children's children might be able to view in a world that's going to be very short, eventually, of those things," he says.