A lot of people would like to remove things from wrecks based on the idea that it's going to be covered up by zebra mussels anyway, or somebody else will steal it anyway. But once you take an object from where it's been for 50 or 100 years, it's usually a death sentence for that artifact unless extensive conservation measures are taken. The problem is both deliberate and accidental intrusion, he said. Divers, for example, have rubbed off ship names on a wreck, thinking it was algae, or caused structures to collapse just by touching or landing on them. Unmarked shipwrecks also are vulnerable to anchor damage from passing boats.
Buoys now mark eight wrecks in Wisconsin waters, and more are being added each year.
Shipwreck divers are attracted both by the sport and the stories that resonate from the derelict hulls. A detailed survey of the Adventure's remains, for example, established that the ship probably burned because of a fire that started in the coal bunker, not in the lime barrels stored on deck, he said. The origin of the fire hadn't been clear when it sank. Unlike archaeological sites on land, shipwrecks freeze a time and place because a sinking ship carries everything to the bottom, usually not allowing time for artifacts to be removed. For that reason, divers can get very involved in the history of their favorite wrecks, Herdendorf said during a workshop here earlier this month.