The community college's survey equipment was donated by Kongsberg Underwater Technology, Inc., a Norwegian company.
Officials have worked for a week to map the bay bottom, and captured sonar images of what's believed to be the sunken Lauren Castle tugboat near Suttons Bay. The image shows a boat with mast sticking up in about 400 feet of water, where it sank in November 1980.
"I think she's sitting straight up and down on the bottom," VanSumeren said.
A submersible remote-operated vehicle with a camera will be sent down to investigate further.
The Northwestern on Wednesday slowly cut through the water about a half-mile southwest of Power Island when a blip appeared on the computer screen.
"That's the wreck of the Tramp," VanSumeren said. "It's very sandy, so anything that's on the bottom really stands out."
The Tramp was a wooden, 54-foot tugboat that sank in the 1970s, and now is a popular diving attraction. It appeared on the sonar screen with a white-shaded area next to it, the "shadow" of the sonar image of the vessel.
"It's like the shadow of a tree. You can tell what a tree looks like without actually looking at it," VanSumeren said.
Sonar equipment sends out sound waves on both sides of the Northwestern at a 45-degree angle toward the bay floor. The sonar "shadow" was created as sound waves bounced back from the sunken tugboat.
The sonar even picked up schools of whitefish that appeared on the computer screen as clusters between the bottom and the bay's surface.
"How can you not be fascinated by this? This is awesome," said Jack Rowell, of Kalkaska, a potential NMC student.
Rowell was along for the ride on Wednesday to get a taste of NMC's freshwater studies as he tries to decide between that program and the college's Great Lakes Maritime Academy.
Rowell was laid off from a machining job in Kalkaska and wants to complete training to find a new career.
"I'm definitely interested in this. I'm interested mostly in getting a job," he said.