On July 15, 1914—almost exactly a year before the Eastland disaster—the Silver Spray ran aground on Morgan Shoal, just a few hundred feet off Hyde Park’s 49th Street beach. The 109-foot passenger steamer was on its way to pick up 200 University of Chicago students and take them to Gary, Indiana, to tour the steel mills; according to an article that ran the next day in the Chicago Examiner, the cook was making a stew at the time and the seven-man crew refused to abandon the listing ship.

Today that boiler is still visible from the beach, a boxy metal structure rising a few feet above the top of the water. From the shore it’s easy to mistake for a rock or chunk of concrete, and for years I saw it without giving it a second thought. Last August, on a bike ride with a friend, I passed the concrete blocks that separate the beach from the Lakefront Trail and noticed a sign colorfully markered on a dry-erase board: shipwreck tours 10:30-noon, free.

On that August Sunday, Lane showed the assembled handful of people black-and-white photos of the ship and a hand-drawn diagram of the pieces scattered on the shoal, explaining that on this part of the lakefront the water deepens to about 20 feet very quickly as you move away from the shoreline, then becomes much shallower on the shoal, ranging from about three to ten feet. He’d brought snorkel masks and fins for people to borrow, though for legal reasons he said he couldn’t officially lead people out to the wreck. But he was going to swim out there, he said, and wouldn’t stop anyone who wanted to follow him.

Exploring the remains of the wreck last summer, I understood what had fueled Lane’s fascination with it. There may not be much of the ship left, but what is there feels—cliche as it sounds—like a hidden world. Finding even a small piece of twisted metal on the bottom of the lake felt like a major discovery, and while the plant life and fish on the shoal may pale in comparison to the Caribbean’s flora and fauna, investigating it was still fascinating.

“What motivates me the most is when I see institutions in power exercising that power without public input or participation,” Lane says. “It’s classic of powerful politicians like former mayor Daley.”

Plotner, like Lane, believes the shoal is unique. “There seems to be more biodiversity there than elsewhere in the lake,” he says. “I’ve seen fish there that I have not seen elsewhere.”

Five other historic shipwrecks—and perhaps some preserved corpses