There is a deep hole up near the Oh, Michigan and Ontario border convergence but do not have any GPS numbers for it. Only had a Sitex Loran C at that time and have been unable to find it since way back then, I have been over it twice long ago in the late 70's. I don't believe it is 100 ft. deep though but closer to 70 ft. and the area is not very big. It is possible it is in Canada or even Michigan as there was no way of telling exactly where the border was at that time while on the water. But it is in that area.