The French sailors' spirits must have been running high as they headed out onto Lake Superior on that November day 99 years ago.

After a long journey from France in what would turn out to be the waning days of World War I, the 100-plus men made up the crews of three brand-new minesweepers built for the French Navy at a shipyard in Fort William, Ontario (now part of Thunder Bay).

The Cerisoles, Inkerman and Sebastopol - named for French military victories of past centuries - were finally complete and ready to sail for Europe. On Nov. 23, 1918, with crews of 38 and a Great Lakes pilot aboard each deck gun- and wireless-equipped vessel, they motored down the Kaministiquia River and out onto the big lake, past the Sleeping Giant, around Isle Royale, heading toward the Soo Locks.

Only one made it.

A wicked Lake Superior gale hammered all three of the ships as they crossed the open lake on the night of Nov. 24, with the ships desperately trying to reach the relative shelter in the lee of Michigan's Keweenaw Peninsula.

The storm-battered Sebastopol, in the lead, made the turn and limped into Sault Ste. Marie a couple days later. The Cerisoles and Inkerman, and the 78 men they carried, vanished into the snow and spray and were never seen again. Combined, it's the greatest loss of life in a Lake Superior shipwreck.

"Their fate is one of the great unsolved mysteries of the Lakes," said maritime historian Frederick Stonehouse of Marquette, Mich., whose book "Went Missing" includes the story of the two missing ships. "How do you lose two modern, well-built, brand-new French naval minesweepers complete with 38 sailors per boat, Great Lakes pilots, wireless - for all practical purposes, these things are lost without a trace. How does that happen?"

A major new search effort underway this summer is aiming to answer that question.

Weekslong search

For more than a month, a crew organized by the Great Lakes Shipwreck Museum at Whitefish Point, Mich., has been out on Lake Superior offshore from the Keweenaw Peninsula, using modern technology to try to locate the nearly century-old wrecks and solve one of the lake's enduring mysteries.

This isn't the first time in recent years that a search has been launched for the missing minesweepers, but it's likely the most extensive effort.

"To mount an expedition like this is not an easy thing ... but we've been able to keep a boat up there for going on five weeks now," Sean Ley, development officer for the Great Lakes Shipwreck Museum, told the News Tribune last week, with more searching to come.

Among the challenges that have kept the ships' location hidden for nearly 99 years: While they were last spotted near the Keweenaw, they could be just about anywhere in a vast section of the lake. And, Ley noted, the lake in the main search area is "very deep, and also troubled by magnetic anomalies that can affect our sonar" - along with tumultuous topography on the lakebed.

Tom Crossmon, who lives in Hermantown and is a former captain of the St. Louis County Rescue Squad, is lending his sonar expertise to the effort, having previously worked with the shipwreck museum on other projects.

Crossmon said Friday that the weather hasn't been the most cooperative for searching, with some very windy days, "but once we're searching it's been great. ... We're getting a lot of area covered, and eliminating area is every bit as important as having the right area. We're narrowing our search."

Whether or not the minesweepers are located, the shipwreck museum is using this summer's search as a learning experience for possible future projects.

"If we do well with this, even if we don't find them - this is teaching us how to conduct an expedition," Ley said.

'Scary beyond understanding'

It very easily could have been three minesweepers that went missing in that violent November storm back in 1918. Citing an account from the master of the Sebastopol, Captain Leclerc, the News Tribune reported on Dec. 6, 1918, that the ferocious southwest gales "forced them to turn into (the wind) in order to avoid swamping. They were compelled to make a turn to avoid Keweenaw Point. ... The Sebastopol weathered the turn but not without opening her seams and rendering constant use of the pumps necessary."

Add to that the relative inexperience and limited training of the sailors - on new and unfamiliar boats, on waters where the waves are more punishing and less predictable than the ocean swells they may have been used to. With rivets popping below deck, and water seeping in, "it would have been scary beyond understanding," Stonehouse said.

When the Sebastopol finally arrived at the Canadian locks at Sault Ste. Marie, Stonehouse said, Leclerc was surprised the other ships had not arrived - but not yet concerned.

"He left word with the lockmaster, 'when they turn up, tell them that I've proceeded on to Montreal,' fully expecting those vessels to follow. And it wasn't until a couple days later when - 'where's the boats? Why aren't they here?' - that the realization is made that something has happened to them," Stonehouse said.

There were no distress calls picked up from the Cerisoles or Inkerman. While the ships had wireless communications, the News Tribune at the time noted that "their operators were young men and said to be students rather than experienced radio experts" - and may have been unable to operate the radios in stormy conditions, if the equipment was still operable.

The ships had sailed amid some wartime secrecy, but once it was determined they were missing, a full-scale search was launched. In Canada and the U.S., crews scoured the Lake Superior shoreline for signs of the missing minesweepers. Nothing more than a few small items of wreckage possibly linked to the ships was ever found.

In the absence of facts, rumors abounded in the days and decades that followed: Rumors the crew was stranded on a remote island. Rumors the ships were poorly built.

As to the latter, Stonehouse notes that several of the minesweepers' sister vessels had lengthy careers; in total, 12 of the approximately 150-foot-long ships were built by Canadian Car and Foundry in Fort William. And it's unlikely that naval inspectors on-site at the shipyard would have allowed shoddy workmanship to pass.

As with other shipwrecks on the Great Lakes, he said, "whatever theory you want to come up with is probably as good as anybody else's."

"If I were to put money down, my thought would be that both of the ships ... simply were overwhelmed by the waves," he said. "They simply could not survive under those sea conditions with the experience levels of the crews that were on board. ... It just goes over. It's capsized, it's gone."

What happens next

If the Cerisoles and Inkerman are located, depending on where they're found, there will be a variety of federal, state or provincial restrictions to protect the site. And on top of that, the ships still are the property of the French Navy, and would likely be considered a French war grave.

"Finding them may in fact be the easiest thing - the hardest thing may be dealing with the find afterwards," Stonehouse said of the sensitive diplomacy that may be required. "The difficulty will be how to handle these things honorably and to everybody's satisfaction."

For its part, the shipwreck museum is conducting the search as part of its mission to document and interpret Great Lakes wrecks.

"For us, it's finding them for the history of it and telling the story," Ley said.

And what a story it would be. Said Stonehouse:

"It is, quite literally, the most mysterious shipwreck left ... on the Great Lakes."

For more information

To learn more about the Great Lakes Shipwreck Museum, or to donate toward the search efforts, go to shipwreckmuseum.com.

Read more about the Cerisoles and Inkerman in Frederick Stonehouse's book "Went Missing."