Japan's Transport Safety Board says the business operator of a sightseeing boat that sank off the coast of Hokkaido last year did not have a proper system in place to ensure safe and sound operation.

The government's safety board has released its final report on the cause of the fatal accident of the KAZU I which occurred off the Shiretoko Peninsula of the northern prefecture in April 2022. Twenty people were confirmed dead, and six others remain unaccounted for.

The report says the KAZU I was likely sailing with its hatch cover at the forward deck off the latch, and the hatch opened as the boat swayed amid bad weather, allowing seawater to flow in.

It also says that holes in bulkheads, which separated below-deck space and the engine room, caused the entire vessel to become flooded.

The safety board believes that the hatch cover became dislodged, hit and broke a glass window of the cabin, letting in a huge amount of seawater, and accelerated the sinking.

The report says that the operator decided not to suspend its services despite deteriorating weather because it did not have any staff who could assist the captain with insufficient knowledge and experience.

The report points to accountability of the company's president, Katsurada Seiichi, who should have had knowledge as the one in charge of overseeing the safe operation of the boat.

It says the absence of a safety control system within the company had seriously affected the operation.

The report also says that an inspection conducted shortly before the accident by the Japan Craft Inspection Organization was insufficient, as its inspectors had only conducted visual checks, and failed to find the problem with the hatch through manual checks.

The local bureau of the transport ministry is also pinpointed for its failure to notice problems with the operator during its audit.

As a conclusion, the report says that safety measures taken after the accident should be thoroughly implemented to prevent a recurrence.