An empty cooler!!!!!!!
No, I have seen some spooky things.
3' of bow of an old wood Chris-Craft sticking up out of lake erie that had just recently sunk.
A helicopter sent out to chase me and my Dad out of the firing range of Military reserve base - because we got lost running his 24' Reinel through 10-12's across the lake in late November for winter storage.
The final trip of my first boating season - I was 10.
But, ya got me beat with a surfacing Sub!!