HILLSBURN, N.S. -- The Mounties say they are planning to use a towed sonar system to try and locate a scallop dragging vessel that went missing last week in the Bay of Fundy.

On Tuesday, however, three-metre swells off southwest Nova Scotia delayed the effort.

The body of one crew member, Michael Drake of Fortune, N.L., has been found along the coast north of Digby, but the five other members remain missing after a week of ground and aerial searches.

Crew members Aaron Cogswell, Leonard Gabriel, Michael Drake, Dan Forbes and Geno Francis as well as captain Charles Roberts were on board the Chief William Saulis when an emergency beacon signal was received at 5:50 a.m. on Dec. 15.

RCMP spokesman Sgt. Andrew Joyce said in an interview Tuesday the sonar search will begin when the waters of the Bay of Fundy are calm enough to safely operate the equipment -- possibly later in the week.

"We would all certainly like to bring those men back to their families," he said, adding the continuation of the aerial search will be assessed daily. The aerial search was also cancelled on Tuesday due to poor weather.

Lori Phillips, the mother of crew member Aaron Cogswell, said in a Sunday interview she is hoping the search effort will return the lost fishermen to their grieving families, even if it means retrieving her son from the bottom of the ocean.

Joyce, however, said the first step is to locate the vessel, after which assessments of recovery possibilities can occur. "Once that step is achieved, the next step would be no easy feat due to the extreme conditions of the tides and currents and silt in the waters combining," he added.

The tides in the bay are massively powerful, with a single tidal cycle moving about 110 billion tons of water in and out of the Bay of Fundy, posing challenges to remotely operated underwater vehicles and to human divers.

Pierre Murray with the Transportation Safety Board of Canada said the emergency beacon indicated the dragger was about 4.8 kilometres off the coast, in waters about 65 metres deep. He noted it is rare for the safety board to raise a boat in the Bay of Fundy in order to study potential safety issues.

The last time he could remember that happening, he said, was in January 2004, when the 9.7-metre Lo-Da-Kash, based in Maces Bay, N.B., was headed back from Campobello Island in the Bay of Fundy when it sank with three people on board.

The safety board conducted a dive on the vessel in May 2004 and it was raised to the surface four months later and towed to shore. However, that was in waters that were just 30 metres deep at low tide, Murray said.

He said one person on the Lo-Da-Kash swam to shore but was found deceased in the woods. The other two bodies were never located.

In 2008, French authorities funded the retrieval of three bodies from the hull of the cargo vessel Cap Blanc in a recovery effort off the coast of Newfoundland on the Cap Blanc.

Although there was a remotely operated underwater vehicle, or ROV, involved in the preliminary survey of the wreck, divers had to be used to recover three bodies of the crew from St-Pierre-Miquelon in about 130 metres of water. A fourth body was never found.

"I know about that because I was on board the vessel when the operation took place and was on deck when the bodies were brought up to the surface," said Murray in an email.

David Shea, senior vice president of engineering at Kraken Robotics, based in St. John's, N.L., said in an interview Tuesday his company has offered use of its towed sonar systems to the Royal Canadian Navy and to other officials.

Locating the vessel in the bay is a challenge and depends on the quality of the resolution of images taken from the RCMP sonar, Shea explained.

He said the more advanced sonar his company has developed for defence applications can be used to develop sharper images. Sonar, however, cannot provide images inside the hull to determine if bodies are present, he said.

If the ROV can't enter the hull itself and has to cut open the hull, "this requires specialized tooling," Shea said. "For the recovery itself they would probably need a manipulator on the remotely operated underwater vehicle."

Shea said the initial step in a Bay of Fundy recovery is to conduct detailed mapping with sonar to determine the environment the boat is in.

"The first thing you want to do it is map it with a towed sonar system … to get an indication of whether boat is sitting on ledge or on a flat bottom, and whether it is upside down or right side up," he said.

If a recovery is attempted, he said it would be wise to first use a remotely operated vehicle as opposed to humans. "The risk to divers is substantial," he said. "Slack tide doesn't last that long in the Bay so you would really want to know what you're getting into before entertaining sending divers down as well."

Murray said that as of Tuesday, the TSB hadn't determined what category of investigation will be carried out, or if a report will be prepared. He said that determination is made by senior Ottawa officials.

This report by The Canadian Press was first published Dec. 22, 2020.