Saturation diving eyed to salvage sunken sightseeing boat

The Yomiuri Shimbun

16:05 JST, May 3, 2022

Authorities plan to salvage the Kazu I sightseeing boat that sank off the Shiretoko Peninsula.

Wires must be attached to the boat’s hull to enable a crane ship to hoist the vessel out of the water.

However, the boat is on the seabed at a depth of 115 meters, where most divers cannot reach.

A special technique called saturation diving will likely be used to attach the wires. The work will be performed by divers who adapt themselves to high-pressure conditions in advance.

According to experts, saturation divers first inhale a helium-oxygen mixture in a sealed deck decompression chamber on a specialized vessel before spending about a day adapting themselves to the pressure equivalent to that of the site where the sunken ship is located.

The divers then descend underwater in a submersible decompression chamber to reach the site, where they exit the chamber to perform the work.

The procedure requires advanced technology and special equipment, and only a few companies in Japan can conduct such work.

“The search using underwater cameras has proceeded with difficulties,” said Hidetoshi Saito, president of the Society of Water Rescue and Survival Research. “Wires can be attached to the hull using a remote-controlled underwater drone, but there is a greater chance [of success] if companies specializing in saturation diving perform the work.”