A Japanese tourist coast guard says, a tourist boat is missing off the northern part island of Hokkaido.
Report says, authorities lost contact with the vessel, which had 26 people on board, after it sent a distress signal saying it was taking on water at 13:15 local time on Saturday, as four people have since been found and have been taken for medical attention.
The boat, Kazu 1, is believed to have been on a three-hour sightseeing voyage around the Shiretoko Peninsula.
The area is a designated UNESCO world heritage site, and boat trips are popular with tourists hoping to spot whales and sea lions as well as brown bears on the rocky beaches.
Coast guard says it has dispatched patrol boats, police and military aircraft to find the vessel,as well as local fishing boats to join others for the search.
According to Japanese media, Kazu 1 was last heard from at around 15:00 local time when the crew said it was tipping at a 30-degree angle and starting to sink.
Waves in the area had been high and local fishing boats had apparently decided to return to port by mid-morning.
The crew reportedly said that out of 26 on board, there were two crew, and two children on board as they all were wearing life jackets.
But temperatures in the area could dip as low as 0C, 32F, when night falls.