It was dark, it was cold, and it was very, very deep.
The date was January 23, 1960, and two men had just become the first humans to descend to the deepest spot on earth: the Challenger Deep of the Marianas Trench in the South Pacific. At nearly 36,000 feet, the trench is deep enough to swallow Mount Everest whole -- with nearly a mile of water to spare!
If not for a special, heavy duty submarine named the Trieste, the immense weight of the water would have crushed the two deep-sea sailors, U.S. Navy Lt. Don Walsh and Swiss scientist Jacques Piccard. Amazingly, however, the two explorers could see curious fish and glowing crustaceans swimming just outside their submerged vehicle, perfectly at home in the high-pressure habitat. It was also inky black. "Once you get down beyond 500 feet, it's pitch dark," Walsh recalled to a journalist a few years ago.
As NATURE's DIVE TO THE ABYSS shows, Walsh and Piccard weren't the last explorers to visit the sea depths -- although they still hold the record for going the deepest. Since their historic dive, a fleet of state-of-the-art submarines, both manned and remotely controlled, have allowed researchers to explore ever more of the hidden world beneath the waves. On DIVE TO THE ABYSS, for instance, viewers can watch these amazing craft -- including Russia's MIR, one of the deepest-diving manned subs in the world -- as they probe three fascinating seascapes: the Mid Atlantic Ridge, California's Monterey Bay Canyon, and the Cayman Wall at Grand Cayman in the Caribbean.
These modern divers are a far cry from the earliest submarines. Ancient storytellers said Alexander the Great descended into the drink in a glass barrel 350 years before the birth of Christ. But many modern historians credit Cornelis Van Drebbel, a Dutch aide to King James I of England, with building the first practical underwater vessel in 1620. His wooden boat, sealed with greased leather, was tested in England's Thames River, but couldn't go very far.
Today's steel and alloy craft are far more capable. Russia's two MIRs, for instance, each can take 2 or 3 people down to 20,000 feet -- journeys that can take 8 or more hours to complete. Japan's Shinkai 6500 and France's Nautile can go equally deep. And the United States' Alvin, while able to descend to just 15,000 feet, has produced a slew of landmark discoveries, such as giant tube worms that live on chemical-rich waters spewing from volcanic vents. It's also plucked lost hydrogen bombs from the bottom of the sea, helped discover the wreck of the Titanic -- and even been attacked by a swordfish, which got stuck in the craft's side!