On the DTE aerial photo site in the 1961 aerial imagery I noticed that there are a number of photos which extend into the lake. The one furthest south has a boat in it with some weird looking attachment connected to the end of it which extends for some distance. At the end of the attachment it appears there appears to be something dispersing out of it. The only idea I have is that this may be near the dumping grounds found on many charts of the lake which is where they discharged the sediments from digging the shipping channel.

Image: http://www.clas.wayne.edu/photos/par.../fm-36-129.pdf

1961 Macomb Page: http://www.clas.wayne.edu/photos/par...omb61Index.pdf