• Rahul Rao

Twenty Thousand Leagues Under the Sea

by Rahul Rao, Varun Rao and Yasir Aheer


  • Despite the proximity of deep seas, their exploration has received much less scientific and popular attention than that of space.

  • Deep seas are a completely alien environment and are home to many strange and fantastic creatures.

  • Exploration of the Mariana Trench, the deepest part of any ocean, has been difficult and sporadic; humans have been there fewer times than to the moon.

  • With remotely operated vehicles taking over exploration of the shallower seas, this technology is being “depth-proofed” to facilitate less risky exploration of deep seas.

  • Most of the ocean remains unexplored - will that change?

We have previously explored the incredible story of man’s reach upwards to the heavens. What little kid doesn’t dream of space and what young adult isn’t enamoured of Neil Armstrong’s first words upon setting foot on the moon - “One step for a man, a giant leap for mankind”? Compelling as that story is, popular comic books from that era talk of aliens, space monsters, and strange planets teeming with life but reality failed to deliver on that score.

Imagine if it had succeeded. Dream of a world with fantastic creatures, environments utterly alien to our existence, and a whole ecosystem that would be unthinkable to us now. Giant monsters do battle while puny human explorers barely register on their radars. Small, strange animals scuttle around taking turns at being predator and prey, while humans gaze in awe, protected from the elements by space suits. The oxygen-poor atmosphere requires the intrepid explorer to bring their own supply of oxygen. Acutely aware that humans are unwelcome guests in this alien world, the explorer lives in fear of his oxygen supply being cut off or becoming prey to a celestial superpredator himself.

With some small modifications, this world does, indeed, exist. Look not to the heavens but down into the inky depths of the deep seas.

(A) Leafy sea dragon with unusual appendages to camouflage itself as seaweed, (B) Japanese spider crab that grows up to 12 feet from claw-tip to claw-tip, (C) Goblin shark with its extendable jaws, (D) Anglerfish with its bioluminescent “bait”

Deep seas

Deep seas are the parts of the ocean that are greater than 1800m in depth, where heat from the sun cannot reach and darkness is all-pervasive. These depths experience more than 1000 times atmospheric pressure and, without heat from the sun, hover around 0 degrees Centigrade. This, then, is no place for the faint of heart.

As is human nature, the exploration of deep seas was always a matter of “when”, not “if”. Initial attempts were rudimentary, limited to the “sounding” of deep water - the technical term for determining the depth of a body of water by tying a lead weight to the end of a string and lowering it till the bottom is reached. The earliest recorded sounding attempts in truly deep water were in around 85BC off the coast of Sardinia when Posidonius reported 1000-fathom (1830m) depths. In more modern times, Magellan tried to sound the Pacific Ocean in the region around French Polynesia in 1521 but gave up when a 750m sounding line failed to find the bottom.

In 1818 Sir John Ross dredged up the first known deep-sea life from around 1600m while exploring around Baffin Bay. This discovery opened up an interesting question - what sorts of life forms could survive the immense pressures of the deep seas? Would we find only worms and jellyfish? Or were there larger, more evolved monsters lurking?

The first series of expeditions arranged primarily to explore the deep seas were run between 1872 and 1876, operating off the HMS Challenger. Challenger was an old warship repurposed for that most noble cause - the advancement of human knowledge. The sheer number of species found on those voyages was breathtaking. Little were they aware that their findings would be used as supporting evidence for the greatest challenge of the 21st century, global warming. The painstaking thoroughness of these early expeditions were difficult to improve upon in the decades immediately following their conclusion.

Until, that is, the invention of the bathysphere and its successor, the bathyscaphe. In 1930, an expedition led by William Beebe used a bathysphere to descend to 803 feet, breaking the 525 feet record of the time. To most people of today, a bathysphere looks like a terrifying metal coffin - a 5-foot metal sphere with three tiny Perspex windows and inch thick walls. The bathysphere was lowered off a surface vessel by a steel cable, carried two oxygen cylinders on board, and had a phone line to the outside world running alongside the steel cable. To William Beebe and Otis Barton, the first divers that used it, it was a gateway to a different world.

William Beebe peering through the entrance of the bathysphere

Over the next few years the bathysphere dived ever deeper and was used for a myriad of biological studies. In 1934, Beebe and Barton reached a new record depth of 923m. New species of deep-sea life were found and painted by Else Bostelmann, the expedition’s artist. Some of these species looked like they had been dreamt up by HG Wells or Arthur C Clarke. A sample of some of the weirdest and most wonderful of these animals is shown at the beginning of this article. Some astonishing displays of their bioluminescence, narrated by the incomparable David Attenborough, can be seen in the video below.

Race to the bottom

The next major breakthrough came with the bathyscaphe Trieste, designed by Swiss inventor Auguste Piccard. Similar to the bathysphere, the bathyscaphe was tiny and spherical and had incredibly thick walls to withstand the immense pressure of several thousands of metres of water. Unlike the bathysphere however, the Trieste had detachable ballast weights and a massive gasoline-filled buoyancy tank attached to it, allowing it to dive and surface without having to be tethered to a surface craft. In 1953 the Trieste dove to 3150m, setting a new world record.

Although this feat was quickly surpassed by the French FNRS-3 in 1954 (4050m), the Trieste was later bought by the US Navy with the intention of using it to reach the deepest known part of the Ocean - Challenger Deep in the Mariana Trench near Guam. On 24th January 1960, the Trieste, with Jacques Piccard and US Navy lieutenant Don Walsh aboard, began its descent into Challenger Deep. Five hours later it hit the bottom of the sea floor, approximately 10,912m below sea level - the deepest any human had gone and will go for the foreseeable future.

Trieste spent 20 minutes on the ocean floor with its two bathynauts looking out into the murk stirred up by the landing. “It was like looking into a bowl of milk”, recalls Walsh. They dropped their ballast and began the three-hour ascent to the surface in silence.

At the time, Walsh thought no more than a couple of years would elapse before the next intrepid explorers descended to Challenger Deep, with better torches and instruments to peer at the strange world that he had the merest glimpse of. In an eerie parallel to space exploration, nothing of the sort happened. Instead unmanned craft took over exploration of the deepest seas and the next time a human being set foot in Challenger Deep was 50 years on, in 2012 when famous filmmaker James Cameron piloted the submersible Deepsea Challenger to 10,912m below sea level.

Much of undersea exploration is now performed by Remotely Operated Vehicles (ROVs). The Monterey Bay Aquarium Research Institute has developed two ROVs to explore the ocean floor and collect samples of sediment, flora, and fauna. The video below shows the incredible detail captured by the ROV’s cameras and the delicacy with which samples are handled by the manipulator arms.

The marvellous Stanford Robotics Lab takes this one step further with OceanOne, a humanoid ROV that explores shipwrecks. OceanOne boasts haptic sensors on its robotic arms that enable a human sitting at a computer to feel their way around real pieces of long-lost history such as La Lune, King Louis XIV’s flagship that sank in the Mediterranean in 1664.

In many ways, ROVs make a great deal of sense in underwater exploration when the cost of human life is taken into account. Accidents are not uncommon and when they occur, the chances of rescue are low. The risks and consequences assume greater significance when exploration happens in the truly deep seas. In this endeavour, the Japanese have made more headway than most. Their ROV, the Kaiko built by Mitsui, was a $50m effort that made it to the bottom of the Mariana Trench thrice between 1995 and 1998. Sadly it was lost at sea in 2003 during a typhoon. In 2009, Nereus followed Kaiko and became only the third vessel to ever reach the bottom of the sea. Will more follow or, as with space, has Man’s fascination with the deep sea been lost?

Looking ahead

It is commonly known that approximately 71% of the surface of the Earth lies under water. Much more astounding is the fraction of all living space on Earth that is contained under water - an incredible 95%. The variety of environments in that 95% is also stunning - from shallow continental shelves to deep seas, warm tropical waters to iceberg-filled fjords. Of this, more than 80% remains unexplored. We know more about the surfaces of the Moon, Mars and Venus than we do the ocean floor. Will that ever change? Or is the most alien, inhospitable landscape we know actually in our own backyard?


Disclaimer: This article is based on our personal opinion and does not reflect or represent any organisation that we might be associated with.