Shinkai 6500 dives reveal deep-sea mysteries

The Yomiuri Shimbun
Shinkai 6500, a manned submersible for academic research, is hoisted by the crane aboard its home vessel, the Yokosuka, in Suruga Bay off Shizuoka Prefecture before descending to a depth of 3,500 meters with a three-member crew.

A massive crane on the back of a ship hoisted the Shinkai 6500 manned submersible up into the air and lowered it onto the surface of the sea. The underwater research vessel for the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) then slipped under the waves to explore the ocean’s depths, descending at a rate of 45 meters per minute.

The Shinkai 6500 can dive to a depth of 6,500 meters, which makes it valuable for exploring our watery planet. About 70% of the Earth’s surface is covered by sea, about 90% of which is said to be 200 or more meters deep.

At 6,500 meters below sea surface, the water pressure is equivalent to the weight of a compact car resting on an area the size of a fingertip.

The submersible has helped researchers study earthquake mechanics, marine life and other areas of inquiry on nearly 1,600 missions without incident since it was first used for underwater research navigation 30 years ago.

The Yomiuri Shimbun
Pilot Toshiaki Sakurai, right, checks equipment inside the cockpit of Shinkai 6500 together with the other crew members before the vessel submerges. Three observation windows plus a variety of meters, gauges and oxygen tanks cram the cockpit, which is a spherical pressure hull made of a titanium alloy capable of withstanding massive water pressure. It was Sakurai’s last underwater mission before retirement.

“[The Shinkai 6500] has responded well to the inquisitive nature of researchers wishing to see things with their own eyes,” said Toshiaki Sakurai, 61, the vessel’s pilot, who has taken part in 432 underwater missions, including some utilizing the Shinkai 6500’s predecessor.

The cockpit of the vessel has a diameter of 2 meters and can accommodate a maximum of just three people: two pilots and one researcher.

Sakurai, who retired as a frontline pilot after his last underwater mission in March, was witness to many important findings, such as the discovery of a new species of giant squid in the Indian Ocean and a huge fissure in the seabed near the epicenter of the 2011 Great East Japan Earthquake.

The Shinkai 6500, with its near-impeccable track record, has also been used in studying the negative impacts of plastic refuse on the environment. The vessel has found a large amount of plastic shopping bags, food packaging and microplastics (particles measuring 5 millimeters or smaller) at the bottom of the nearly 6,000-meter-deep sea off the Boso Peninsula in Chiba Prefecture. The discovery revealed a shocking amount of waste piled up deep in the ocean by the Kuroshio current.

Shinkai 6500 has recently been used in a new role as part of a navigation experience event in which university students and others are offered the opportunity to board the vessel. The program is aimed at finding new talent in marine research fields.

“The sensation and experience of seeing something with your own eyes is beyond valuable,” said Ken Takai, 51, a senior researcher at JAMSTEC. “I hope they will get a sense of an unknown world — a world that can only be reached with Shinkai.”