Something went wrong in 'San Francisco Bay. What caused the dangerous boat to sink?

James Smith, a veteran sailor and captain of the chartered fishing boat California Dawn, was sailing under the Golden Gate Bridge on Tuesday when he heard a call on his radio: The ship was in distress off Alcatraz Island.

In the distance, Smith saw what looked like smoke or smoke rising from the water. As he ran to the scene, he saw that a large motorboat was sinking rapidly. Other passengers were clinging to the hull of the partially submerged vessel, he said, while rescuers administered CPR to a man in a San Francisco police boat.

“Something went wrong with the boat for it to go down like that,” said Smith, who has operated charter boats for 35 years. “It's not just that the wave hit it and it just turned.”

Rescue teams scrambled to pull 17 people to safety, but after reaching shore the man who was given CPR was pronounced dead. On Thursday, the woman on board was found in the harbor and pronounced dead. Two passengers are still missing.

As search teams continued to scour the harbor Thursday for missing passengers and the remains of the sunken ship, it is not yet clear what caused the 49-meter, three-decker boat to flip on its side and fall into the water.

According to Captain Jarod Toczko, commander of the US Coast Guard in San Francisco, survivors reported that a wave hit the boat, causing it to list heavily and capsize suddenly.

But investigators and maritime experts, including the captain who was out of port that day, told The Times that a single wave would not have caused such a large vessel to sink. Although the exact cause will not be known until officials take the boat out of the sea and carry out a full investigation, they said that the ship, which was carrying 20 passengers in memory of a loved one, probably entered the water after a series of problems or failures.

Although the water was receding Tuesday afternoon, Smith said, it wasn't too bad. He estimated that there was probably a 4 meter wind chop and said that the small boats in the water were fine. In such conditions, a 49 meter boat can generally be stable and 20 passengers cannot be expected to overload it.

He noted that the boat had already run into rough waters that day – passing under the Golden Gate Bridge into the Pacific Ocean before returning across San Francisco Bay to Angel Island – before returning to safer ground.

There are many things, Smith said, that could have caused the ship to run aground as it headed back into the San Francisco Bay. The boat – called Volare – could have lost the water line that cools the engines, he said, or lost the steel shaft that transmits the engine's rotational power to the propeller to drive the boat forward.

“I think he lost a line where he's cooling,” Smith said, referring to the blue water line that pumps water to cool the engine and returns it back to the back of the boat. He said that might explain the steam rising from the boat. In a boat of that size, he said, the line might be about 1½ inches or 2 inches.

“A 2-inch hole in your boat, it doesn't take long for it to start filling up,” Smith said. “You're on a trip, you have a bunch of people, there's a lot of noise, maybe the boat is shaking and you don't even realize it's too late.”

With Alcatraz Island in the background, flowers float in San Francisco Bay as search and rescue operations continue for the missing victims of a ferry that sank on Wednesday in San Francisco.

(Noah Berger/Associated Press)

Randell Sharpe, a Bay Area marine accident investigator, agreed that a wave probably did not cause the boat to sink. Likely, he said, there are many factors that combine.

“For a ship that big to capsize, it's not going to be just one wave,” Sharpe said, noting that photos and videos from the scene showed the water was rough, but not strong enough to overturn a large boat.

The waves would have pushed the ship forward, Sharpe said. But even then there would have to be holes – in the holes or sides of the bottom rooms or some failure in the engine room – which would allow more water and make the boat lose stability very quickly.

He said one photo of the boat shows seven windows along the main deck. He said if the windows had been open, the boat could have taken on a lot of water when it started rolling.

“Were the windows open?” Sharpe said. “Did they find another source of the leak in the engine room, maybe a pipe to one of the engines, or a drain pipe, or something that allowed water to get under the water line?”

He said that if there is a problem, the distribution of passengers on the boat can exacerbate the problem: too many people on top can make the boat too heavy.

According to the survivors, Toczko said, some passengers were below the ship but many were on the main deck when they encountered problems.

“Did everyone stand on one side of the boat, facing the front of the city?” Sharpe said. “That can disrupt the ship's stability, so you tend to move forward there.”

After looking at the boat's tracking data, Capt. Jim Elfers, a Bay Area marine surveyor who provides damage assessment and boat safety inspections, said that as the boat left Ayala Cove on Angel Island, heading back toward the city's edge, it may have fallen victim to a debilitation effect called “sea effect.”

“It's a cyclical roll that's set up when the boat takes a 4-foot wave repeatedly over the frame,” Elfers said, referring to the widest part of the boat's hull. “It sets the roll, and in this case, the center of gravity of this boat may have gone up a lot. [20] passengers on a 50 meter boat, especially if they are all very tall, you have a center of gravity that goes up. He discovered that the boat enters a cyclical line.

If a single large wave were able to enter the decks, which is rare in San Francisco Bay, Elfers said, that could present problems if the boat is not watertight: Water could find its way to any vulnerable spot or anywhere it's not sealed off and enter the hold and start a negative flow that can make the boat unstable and slowly sink into the water.

“And the next wave comes, the next wave comes, and all of a sudden you're in flux,” Elfers said. “It's like if you have a child on a swing, you can push that child with two fingers a little, but little by little you can get to the point where you're already rolling on that swing.”

After being a licensed captain for 35 years, Elfers said he was always careful, if he started to see the beam sea effect and there were many passengers on top, to move people down to the house.

“Usually you'll get a warning, because the boat is starting to capsize, but it's not bad yet,” he said. “That's the time when you're trying to move people and lose weight. I personally would say, 'Hey, look, it's going to take a little bit here for about the next 20 minutes.

Elfers also said that it is very common for a boat engine, which does not have a closed cooling system like a car, to have a leaking hose or a failed hose clamp.

“Something fails, and the engine itself starts pumping water into the engine room,” he said. “That has become a common occurrence because the engine is always pulled into the sea to cool the engine.”

It is not clear how the boat, registered in Stockton, was maintained or inspected before this week's trip.

According to the San Francisco Chronicle, John Boisa, 62, is the ship's owner and captain. He was the younger brother of Clifford Joseph Boisa, the passenger who died in the incident. A family member told the media that his brother was an experienced sailor.

“He was an officer in the Navy and he knows how to handle a boat,” his brother, Ralph Boisa, told CBS News. “He has been out to the harbor and the Golden Gate and down the coast many times without any kind of accident.”

Smith said he could only speculate about the boat's maintenance or the experience of the captain, noting that it was a private boat.

“I hate to guess because boats can sink in an instant,” Smith said, noting that he's had “all kinds of weird things” happen in his 35 years at sea. “Maybe some kind of fluke happened.”

People should always be careful when they're out in the water, Sharpe said.

He said: “You have to do regular maintenance on a boat. It's not a car you can take every six months or once a year to change the oil.”

“Until the Coast Guard raises the boat, or they come out with another preliminary investigation, it's anybody's guess.”

On Thursday, divers from the San Francisco Police Department's Marine Unit, in close coordination with the US Coast Guard and other partners, conducted a grid search of the vessel, which is believed to be 120 meters deep in the rocky sea, using boat-mounted sonar platforms and other equipment.

Once the vessel is located and properly identified, the department said in a statement, it will work with the US Coast Guard and other partners to assess recovery options and determine whether it can be recovered at sea.