When Bob and Shirley Hansen anchored their fishing boat off the coast of Southern California, they were prepared for a quiet night. But they awoke in the middle of the night to frantic knocks — and soon discovered five men, soaked and shivering, who had managed to escape a burning dive boat several hundred feet away.

The boat, Conception, was anchored just 20 yards off the Channel Islands when it caught fire early Monday. The 75-foot vessel carried dozens of divers on a holiday excursion, many of whom were asleep in their bunks below deck when the fire broke out.

The Hansens pulled the five survivors, who had been awake and on the boat's bridge at the time of the fire, onto their boat. The group included the ship's captain, who told them that a rear escape hatch was engulfed in fire and that the crew could do nothing to help the passengers. 

One crew member was inconsolable, telling the Hansens that three passengers were celebrating birthdays — including a 17-year-old there with her parents.

"He was crying, because he knew they were still on the boat," Shirley said. 

"And one of the crewmen, his girlfriend was also on the boat," Bob said. "And she was down there." 

"The flames, and knowing that there are people on board that cannot get out — you can only imagine the horror that they were going through," Bob added.

The Hansens said some of the crew tried to go back and search for others who may have survived, but they couldn't find anyone.

According to the U.S. Coast Guard, at least 25 people were killed in the flames. Nine remain missing. Authorities say the company operating the boat had a good safety record.

"At first you feel helpless, but now, you know, it's settling in," Bob said. "You know, it's one of those things you just can't unsee."

The National Transportation Safety Board is sending a team to investigate the cause of the fire, and the FBI is also assisting in the investigation. Officials say the ship is unstable and upside down in about 60 feet of water, making it more difficult to find and retrieve any bodies that may still be inside.

The Hansens said their own daughter has gone diving on that boat before, and that they have a family friend who was a dive master who did not make it out. Rescue operations are still ongoing, as family members of the nine people still unaccounted for wait for answers.

Related: 2 Students From Elite High School Victims In Deadly California Boat Fire