June 5, 8:00 p.m. ET

“Superior Maximus, here we come!”

Seated at the wheel of the Tale Spinner, Jocelyn Bentley pushes the throttle forward as far as it can go, and the small aluminum landing craft surges across the glassy surface of Lake Superior. A monitor displaying a bathymetric chart shows the boat cutting straight down the centre of a submarine canyon marked in darkest purple. As it travels, astonishing depth readings flash up on another monitor: 387 metres. 390. 401.

Bentley is part of a team of documentary filmmakers led by underwater explorers Yvonne Drebert and Zach Melnick who are revealing the unseen depths of the Great Lakes in hopes of raising awareness of the richness and importance of freshwater ecosystems. I’ve joined them in Munising, Michigan for a pivotal moment: tomorrow, the team is planning to drop a cutting-edge ROV into this canyon and stream images of it to the public in realtime. The dive will mark the first time in 40 years that “Superior Maximus” — the deepest point not only in the world’s largest lake by surface area but in all of the Great Lakes, by a long shot — is seen with human eyes.

Bentley and Melnick are sounding the canyon with multi-beam sonar, searching for deep spots and geological features that offer the best chance of delivering on the team’s ultimate goal: to film giant siscowet lake trout and — maybe, hopefully — a kiyi, a deepwater fish found only in Lake Superior and never seen alive in its natural habitat. But their excitement is cut short; weather radar shows heavy thunderstorms moving in on land and out of an abundance of caution, the call is made to return to shore. The decision of where to drop the ROV — fittingly named Kiyi — will have to be made on the fly tomorrow.

Fortunately, a test of the livestream itself earlier in the day went off without a hitch, though Melnick’s script reminds viewers that “this is a real expedition; things may not go perfectly.” Melnick has been obsessively checking the wind and wave height forecasts on Windy.app. Winds stronger than 15 knots would be a no-go; currently the forecast is for winds up to 12 knots by stream time.

June 6, 7:30 a.m. ET

Forecasts this morning are showing stronger winds than hoped for by the time of the stream, but the only way to know for sure if it will be safe to deploy the ROV is for Melnick and Drebert to go out with a smaller crew on the Tale Spinner and assess for themselves. In Munising, it’s foggy and significantly cooler in the wake of yesterday’s thunderstorms, but as I learned yesterday, conditions 55 kilometres offshore bear little resemblance to the weather on land.

The plan right now is for the rest of the team to join Melnick and Drebert at the dive site on the Lake Char, a larger boat operated by the Michigan Department of Natural Resources. Shawn Sitar, a fisheries biologist with the department, is keenly interested in seeing Superior Maximus through Kiyi’s lens. He’s looking for any clues as to why “zombie trout” — emaciated siscowet trout — have been turning up in his nets with increasing frequency over the past few years.

Siscowet trout are a type of lake trout that live in the deepest parts of Superior. They are adapted to have very high body fat content, so to find some weighing only about a third of what a healthy siscowet should weigh is cause for some concern.

“At first glance, it appears to be a famine event,” Sitar told me yesterday. “But we want to make sure there’s not some other issue going on.”

Sitar and his colleagues are also working to rule out disease and contaminants as causes for the siscowets’ poor body condition. Being able to observe the fish in their habitat will hopefully point their inquiry in the right direction.

Sitar said unfortunately, plastic pollution is an all-too-common sight even on remote islands in Superior. Commonly found items include hard hats, likely lost from the ore boats that ply the lake, and Mylar balloons. “You walk along the shoreline, and you can see the chronology of things that get into the lake.”

2:00 p.m. ET

Livestream postponed due to weather

The Lake Char was still churning its way through dense fog, captain Chris Little making liberal use of the horn, when Melnick made the call to cancel today’s stream. Although the Tale Spinner initially encountered calm waters above Superior Maximus, the wind quickly began gusting to 20 knots, which would have made it too risky to deploy the ROV (and too uncomfortable for the team). They’re now aiming to begin the stream at 11 a.m. tomorrow, June 7. 

The team is disappointed, of course, but as Drebert put it, waiting for calmer waters means there’s a better chance of actually enjoying the experience. 

I spent the hourlong cruise on the Lake Char speaking more with Sitar about what he hopes to see at Superior Maximus. 

“It’s an exciting event to see a place that I’ve been researching that I could never see, and [have] just basically been trying to infer, deduce what’s going on down there,” he said. He figures the chances of seeing fish are low, since the lake bottom is not very productive. “But just to see the bottom — the deepest extent of the Great Lakes — is pretty exciting to me.”