Coast Guard investigating whale-watch boat stranding

The Cetacea was tied up in Charlestown Tuesday after it returned from its overnight stranding.David L. Ryan/Globe Staff

The Coast Guard is looking into what caused a Boston whale-watching boat to venture into restricted waters, where it became entangled on a floating cable, forcing 163 passengers to spend Monday night at sea.

Investigators from the Coast Guard’s Inspections and Investigations branch are interviewing all parties and examining ship logs, navigational charts, and other records.

“It’s pretty in-depth,” Petty Officer Robert Simpson said Wednesday.

Little information was available about the ship’s route and its contingency plans in case of such an event.

The operator, Boston Harbor Cruises, “made the statements we’re going to make at this time, and we’re just waiting to hear from the Coast Guard about their investigation,” Sheila Green, a spokeswoman for the company, said Wednesday.

The 83-foot Cetacea stalled about 13 miles east of Nahant when its propeller snagged a bright yellow cable for a natural gas pipeline. It was due back at Long Wharf at 4:30 p.m. after a three-hour trip, but that turned into 18 hours after efforts to untangle the cable and transfer passengers failed.

Simpson said the investigation “could take a while.” The ship probably did not have a contingency plan in the event it became tangled in a line, he said. “It’s not something you would expect to happen. Whereas things like a ship fire, taking on water, or a man overboard are things you can absolutely train or prepare for.”

He said that restricted areas, such as the one the Cetacea ventured into, are marked on navigational charts. He could not comment on why the ship was in such an area.

Passenger Stuart Raifman, 66, of Sharon, criticized what he called a lack of preparation and poor communication by the tour company and the officials on board.

“I am legitimately concerned about the safety planning,” he said. “I don’t think there was a plan, and if there was one, I don’t think it worked very well.”

He commended the efforts of two ship interns, who he said tried to keep the crowd updated and comfortable.

“Those two girls deserve a medal and a plaque at the aquarium,” he said. “Meanwhile, we heard nothing from the captain directly for at least three to five hours. . . . He was hardly visible.”

Raifman found the supplies that were delivered by the cruise company wanting. Though blankets were promised, passengers at first received thin sheets and pillowcases that “looked like somebody’s used laundry that had just come out of the dryer,” he said.

The Coast Guard eventually brought blankets, he recalled.

“If I had eight hours and I knew I was going to need blankets, I would go to Walmart,” he said.

Any given moment, he said, many people were vomiting. Some passengers created makeshift ponchos using trash bags. Many were cold.

With potential thunderstorms that night, “We were in a situation that could have instantly turned into something very, very bad,” he said.

Passengers on the ship will receive a ticket refund, ranging from $36 for children to $47 for adults, a $100 voucher toward a cruise on a Boston Harbor Cruises vessel and a $500 check upon filling out some paperwork. The company will also reimburse passengers for approved expenses, such as missed flights.

Hauling the boat to shore and repairing the propeller cost Boston Harbor Cruises $3,000.

“Boston Harbor Cruises’ priority is passenger safety and cruise safety, and certainly the passengers and the crew were safe throughout this whole incident, and what they gave each passenger as they disembarked yesterday, I think was very generous,” said Green, the company spokeswoman.

“I was standing there yesterday as they were disembarking, and people were extremely complimentary of the captain and the crew.”

The cable that snagged the Cetacea was part of Excelerate Energy’s Northeast Gateway Deepwater Port, where liquefied natural gas tankers offload gas, which is then piped underwater to shore. The mooring cable floats on the surface and is marked by buoys.

Boston Harbor Cruises called Northeast Gateway “a valued client” and said the cruise company had expressed its regrets to the owners of Northeast Gateway.