Walking back from the garage (the car was due its M.O.T) I noticed these perched perilously close to the edge of the quay. They weren't there on my return, but hopefully didn't get blown in (strong wind today).
Many years ago, I had a client who was a pig farmer. He once turned up at my office wearing boots like these, except covered in pig s**t.
Clearing up after him was bad, but worst of all was the smell; I couldn't have any more clients for the rest of the day. I also didn't eat my sandwiches at my desk. Needless to say, I made sure there was no chance of him calling again. 
Gumboot facts: the world record for throwing a gumboot (size not specified) is 44.97 metres. The discus record is/was 74.08 metres.
Taihape, NZ, is the gumboot throwing capital of the world, with a Gumboot Day.