The first-ever dive to the deepest spot on Earth happened more than 50 years ago, when, on January 23, 1960, the Bathyscaphe Trieste reached a record depth of 35,800 feet in the Challenger Deep, in the Mariana Trench off Guam -- the deepest point in any of the world's oceans.
Seen here being hoisted from the water by a crane barge during testing by the Naval Electronics Laboratory in San Diego, Calif., Trieste was being prepared for transportation to the Marianas Islands.
As ocean exploration becomes popular, we take a look a some of the coolest, and most unique personal submarines ever.
U.S. Naval Historical Center photograph of R.G. Skerrett drawing from 1902
The Confederate Army's H. L. Hunley
During the American Civil War, the Confederate Army's 7 ton, 39-foot long H. L. Hunley, built from a converted steam boiler, was the first combat submarine to sink an enemy warship.
The sub featured a hand-cranked propeller and one spar torpedo, a crude weapon which was essentially a bomb placed at the end of a long pole, which was rammed into the targeted boat.
The sub was sunk in 1864 in Charleston, South Carolina's outer harbor, and recovered in 2000.
Triton Submarines and high pressure glass fabricator Rayotek Scientific came together to design a full ocean depth submersible that they say will revolutionize man's relationship with the deep blue ocean.
Triton's planned 36000/3 will soon go into production and will be capable of diving to the deepest known point in the ocean, Challenger Deep, in the Mariana Trench, from which James Cameron just returned.
The 36000/3 will be built for deep sea pressures, with features including batteries that sit in oil rather than air, to maintain better pressure balance with the sea outside, and a pressure hull made of silicon glass rather than acrylic.
The company has already produced three of the 33000/3 series "for superyacht owners who want to explore the world beneath the waves."
Deep Flight Super Falcon
Hawkes Ocean Technologies' high performance winged submersible, the Super Falcon is equipped with highly advanced piloting, navigational, and life support electronics, including a heads-up combined graphics navigation and flight display -- a first for privately owned submersibles.
And in case you forget your GPS navigation system on your undersea voyage, the Super Falcon comes with a navigation module and an on-board computerized track plot designed to let the pilot mark way points and to guide the sub back to its launch location.
The DeepFlight Challenger from Hawkes Ocean Technologies was originally commissioned by late adventurer Steve Fossett, who had intended to complete the first solo dive to the depths of the Mariana Trench. With Virgin Oceanic, Richard Branson plans to finish what his friend started and then go on to help explore and unlock the wonders of the oceans still unknown to humankind.
SportSub Solo single person yacht toy
The one-person SportSub Solo is a single person Sub designed as a yacht toy. It weights just 150 pounds, and its maker, International VentureCraft, says the vessel has excellent control and maneuverability, allowing the sub to rotate, hover, and fly straight up and down, just like a helicopter.
SportSub Solo is designed to be operated to a maximum depth of about 33 feet, and for a dive time of up to 1 hour.
U.S. Customs and Border Protection
U.S. Coast Guard; Navy; and Customs and Border Protection crews intercepted and boarded a self-propelled semisubmersible vessel loaded with an estimated $352 million of cocaine on Sunday, Aug. 19, 2007.
These drug smuggling semisubs have an easily detectable heat signature owing to their above-water exhaust, and many were seized in the mid 2000s, leading the drug cartels to replace them with fully submersible subs, which are much harder to detect.
Many smuggling semisubmersibles have been discovered in recent years, but this one was unique. The vessel is more technologically advanced in that it doesn't need to keep an air intake and exhaust pipe above water, making it more stealthy owing to its ability to evade the radar and heat-seeking technology of drug-interdiction aircraft.
Submersible smuggling vessel
The Colombian navy seized this submarine, which was hidden in a jungle area and built to carry up to eight tons of cocaine to Mexico. Soldiers stand guard over the submersible in Timbiqui, southwestern Colombia, on February 14, 2011.
The 100-foot long vessel is capable of traveling about 30 feet below water, Colombian Navy officials said.
Killer Whale submarine
Hammacher Schlemmer's $100,000 Killer Whale Submarine cruises through the water at 50 mph and it can drive to depths of 5 feet. Like a real whale, this two-person sub can breach from the water and features pectoral fins and a 255-horsepower supercharged Rotax axial flow engine.