On the other side of the 4.7-inch diameter, 5.5-inch thick round acrylic window, the bottom of the sea has an ashen hue. A thick layer of sand and dead plankton called marine snow cover the ocean floor.
Inside the Shinkai 6500, pilot Kazuhiro Chiba grips the microphone of an underwater telephone and sends an audio transmission back to the base ship above the waves. Co-pilot Masanobu Yanagitani records the depth and time.
"We have descended to the ocean floor at a depth of one-five-five-three meters,” Chiba says. “We will now commence observation of benthic organisms in the vicinity."
* * *
The Shinkai 6500, a manned research submersible (bathyscape) owned by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), was completed in 1989 and is one of the world's few vehicles that can dive to 6,500 meters below sea level.
Its largest refit to date, costing 690 million yen ($8.57 million) and including an upgrade from four to six thrusters, was completed in March this year.
I was fortunate enough to join a subsequent training voyage.
There were neither waves nor swells at Suruga Bay on the western coast of Shizuoka Prefecture's Izu Peninsula on April 16. The 9.7 meter-long submersible's interior sphere, which is 2 meters in internal diameter and 73.5 millimeters thick, is made from a titanium alloy.
This completely enclosed space protects its passengers from the barometric pressure of the deep sea, and its interior is more cramped than a light automobile. The three of us riding inside are packed in tight, surrounded by instruments.
Just before the hatch is closed, Chiba carefully examines the opening for damage or foreign objects.
"If even a single hair gets caught in the hatch, it'll be a risk deep underwater," he says.
With a splashing sound, the journey begins.
We descend slowly at a speed of 2.4 kph, pulled down by weights of about 1,100 kilograms on the bottom of the submersible. There is no sideways swaying; it feels like riding an elevator.
The pressure within the vessel does not change, so there is no odd sensation in your ears like the kind you get in an airplane. As oxygen from a tank hisses faintly as it flows into the sphere, the numbers on digital readouts change as they display the distance from the surface, the distance to the seabed, and the sea temperature.
I am transfixed to the view port. The sun's rays make their presence felt until around 100 meters below the surface. From there, the water grows darker as if the sun was setting. From 300 meters down, it is 'night' all around.
In the parts of the sea illuminated by the Shinkai 6500's lights, countless tiny particles can be seen.
"It looks like snow falling, doesn't it?" says Chiba.
Around 30 minutes into our voyage, we reach a depth of 1,000 meters. At that moment, a red creature passes in front of my eyes. "Hey, that's a shrimp. There are shrimp here!" I can't help raising my voice.
The barometric pressure has risen to 100 atmospheres, the equivalent of holding a large dump truck in your palm. Here, humans cannot venture outside, no matter what diving gear they might wear. The shrimp, meanwhile, swim along easily.
About 100 meters from the ocean floor, Chiba flicks switches and the submersible releases around half of the weights it is carrying, halting our descent.
It enters a state approaching weightlessness, in which our weight and buoyancy are in balance. To accomplish this, my body weight and even my digital camera were weighed the day before to determine the amount of weights we would have to carry.
From here on, the thrusters kick in, and the Shinkai 6500 begins moving once more.
* * *
I once worked for a company that published a fishing magazine. I would gaze at my fishing line as it disappeared into the deep blue water and become absorbed in thought about the world beneath the surface. I later became a reporter for The Asahi Shogakusei Shimbun for children of elementary school age, and was put in charge of a regular column by television personality Sakana-kun, who is also a guest associate professor at Tokyo University of Marine Science and Technology.
Every week, I was amazed at Sakana-kun’s extensive knowledge. At the same time, I learned that there are fish whose behavior and ecology remain a mystery to us. I wanted to actually travel to the bottom of the ocean to learn more about the world of marine life. On this voyage, my wish came true.
The Shinkai 6500 skims the ocean floor at a speed slower than a person walking. When I press my face against the view port, it feels as if I am swimming with goggles on.
The lights only penetrate the blackened depths for a few meters at most. Suddenly, from out the murky depths in front of us, a creature slithers its way into view. "Ah, that's probably a relative of the conger eel," Chiba says.
A cage on the front of the vessel contains horse mackerel and squid as bait, so the creature must have been attracted by the smell.
After four hours, an order from the base ship resounds inside the vessel. "Shinkai, you are to commence your ascent at one-five-two-zero hours."
Our undersea adventure is over already? As if seeing us off, a bright red Enypniastes eximia (sea cucumber) around 15 centimeters long flutters past our window. Why are there such brightly colored creatures living amid this darkness?
We turn off our lights and begin our ascent. Microscopic organisms that give off light when stimulated begin to glow as they bump off the sides of the submersible one after another. As my eyes adjust, the organisms become visible in greater numbers, and they remind me of watching fireflies dance in the air.
As if slowly mixing blue paint with a pitch black palette, the dark void begins to brighten.
I wonder if it is night or afternoon on the surface. Just as that thought passes through my mind, the sea is abruptly filled with light, and the Shinkai 6500 breaks the surface with a splash.
"Welcome back." Crew members of the base ship greet us with smiles as we emerge from the vessel. Around six hours had passed. Without thinking, I take a deep breath.
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