The 6K to date has conducted over 1,000 dives around the world. During this time, it has escorted more than 800 researchers to depths of the sea without any accidents and contributed significantly to the study of the deep-sea creatures and geology. The 2K was retired in 2004 and has since been displayed at the Yokosuka Headquarters. The operations of the 6K, on the other hand, as the sole active manned research submersible, have been commissioned to the Nippon Marine Enterprises, Ltd.
The 6K is 9.5m in length, 2.7m in width and 3.2m in height and weighs 26.7t (in the air). Its underwater time is eight hours and it takes two- and half hours to reach the depth of 6,500m. It dives by free fall, and can hold three passengers; the pilot and co-pilot who steer the vessel and the researcher.
The 6K team comprises 13 members, of whom eight are pilots and co-pilots, which incidentally is the same number as the Japanese astronauts. One member is Keita Matsumoto (age 38), a First Submersible Technical Officer Mr. Matsumoto joined Nippon Marine Enterprises, Ltd. in 1992 and has gone on nearly 300 underwater explorations both on the 2K and the 6K.

The operating staff of Shinkai 6500. Currently there are 13 members, of whom eight are pilots and co-pilots.

Collecting hot water with Shinkai 6500's manipulator in front of a deep-sea hydrothermal vent, known as "the chimney." (©JAMSTEC)

What is it like on the seafloor at more than 6,000m before the sea surface?
"Generally, light only reaches to depths of 200m and beyond that it is pitch darkness. Beyond the depths of 2,000m living creatures are rarely seen and at 6,000m+, they are even more rare."
Sometimes we come across sights where we can barely believe our eyes.
"A mannequin head was discovered in the rift of the Japan trench." We often find garbage in Sagami Bay, which is over 1,000m deep. "It makes us realize that once you dispose of garbage, it never goes away."

On the seafloor we conduct sampling of specimens and install equipment for research.
"We collect specimens using a vacuum-like device or grab them with an arm, called a "manipulator". The vessel gets pulled back and forth by the terrain and the shifting currents. Landing the vessel in a safe and stable spot takes a certain amount of skill."
The pilots' duties are not limited to steering the vessel. They are also responsible for the daily maintenance.
"It is our pride and joy that Japanese submersible vessels have not been involved in a single major accident."
Sometime Mr. Matsumoto is overcome with emotions, thinking,
"Nobody has ever been here before. Nobody has ever seen this scenery before. I can't help but be filled with a sense of wonder." His dream is to ride on the next-generation submersible vessels.