A staggering 95 percent of the ocean has never been explored. And 99.9 percent of the biological samples taken from the briny deep come from its shallower half. That leaves a vast uncharted realm of reefs, vents, and volcanoes.
1. PHOENIX ISLANDS
It takes a flight to Fiji and a five-day boat trip to reach these South Pacific isles, so it's no wonder they're thought to harbor the world's most pristine coral reefs. Historians are also searching the area for Amelia Earhart's plane.
2. LAU BASIN, SOUTH PACIFIC
One plate of Earth's crust ducks under another here, creating geological chaos and a biologist's playground. The resulting volcanoes and vents can support creatures that endure ultrahot temperatures and total darkness.
3. SOUTHEAST PACIFIC OCEAN
Coral reefs have existed for 450 million years. Still, no one knows how they survive. Biologists would like to find out if, and how, cold-water corals live on the Pacific's undersea mountains - before trawling nets destroy them.
4. TRINIDAD & TOBAGO
Around the islands, oil bubbles up from the seafloor through seeps, attracting masses of critters that chow down on Texas tea. Scientists want to figure out how old the animals are, and if they evolved before or after the seeps.
5. CHARLIE-GIBBS FRACTURE ZONE
The Charlie-Gibbs zone is the deepest part of the Mid-Atlantic Ridge, the world's longest mountain chain. This is where the Earth is born again, literally: Molten rock pours out of the planet's mantle at the fault to form new crust.
6. SCOTIA & WEDDELL SEAS
Sure, 27 countries have outposts in Antarctica, but no one has ever dived to the bottom of these waters. Chunks of seafloor could reveal what the supercontinent was like before it split into continents 180 million years ago.
7. ANGOLA, KAP & GUINEA BASINS
One expedition off Namibia last year snagged 400 new species. Researchers want to visit these nearby basins in which it takes a net 13 hours to settle on the bottom, to see what else turns up.
8. ARCTIC OCEAN
The Arctic is one of the least-explored spots on Earth, and also one of the most important. Climate change affects polar ice first, so deep-sea samples could tell us whether we're due for a global warming disaster.
9. CASPIAN SEA
The southern Caspian has barely been explored, and not because it's far from civilization. Oceanographers want to get a peek at the area's gas seeps, but the Iranian government prohibits most boats from its waters.
10. MADAGASCAR
The waters surrounding the island are filled with creatures that sting and stun. Pharmcos are interested in studying the venomous varmints for chemicals that could prove useful in a doctor's office.
11. INDIAN OCEAN
Far from the world's undersea-research powerhouses, the Indian Ocean is mostly unexplored. But voyages across the surface have hinted at spectacular heat vents along the unmapped ridges below.
12. NANKAI TROUGH
A drilling expedition to Earth's mantle is oceanography's version of a trip to the moon. Japanese researchers want to tap the molten rock found here to better understand earthquakes and volcanoes.
13. NEW ZEALAND
No one has ever seen an adult giant squid alive. But hunters think beasts up to 60 feet long might dwell in the canyons off the Kiwi coast, where cool and warm waters collide and spawn abundant life - and prey.
14. SOUTHWEST INDIAN OCEAN
Every 200,000 years or so, Earth's magnetic field reverses direction. But readings at this spot hint at a 37-million-year stretch when it didn't flip at all. Studying the area could help predict if we're overdue for a reversal.
15. LORD HOWE SEAMOUNT CHAIN, CORAL & TASMAN SEAS
A circle of eroded volcanoes shelters vast coral reefs from high seas. This protected position makes the reefs easy to explore with a deep-sea sub - if only the Aussies had one.
