Boot over troubled water.

There is no rational explanation I can think of for a surgical boot on the parapet of the road bridge over the River Yealm. I first noticed it yesterday early evening and 24 hours later it is still there.I cannot think it was abandoned by the wearer who suddenly can manage without it. Possibly it has fallen from a passing vehicle and has been placed in a prominent position by the finder. My neighbour told me he once found a lawnmower, whilst diving, on the sea bed just off Plymouth breakwater - only 1 mile out to sea!. He was less than impressed by my find.