Went looking for lead sinkers found a brass canon?

The last few days have not been too good so I went out this morning to try and find a bunch of old lead fishing sinkers to melt and cast weights from. I went to Trigg beach and jumped into an area known as the Blue Hole. The Blue Hole is locally famous due to a series of tragic drownings in the late 40's and early 50's most notably those of a nun sister Mary Chrysostom and her would be rescuer Fred Floyd. These drownings prompted the formation of the Trigg Island Surf Lifesaving Club, and it is the clubs proud boast to have never lost a life in patrolled areas, no small achievement considering nearly 50% of all rescues in Western Australia are at Trigg Beach.  Both Sister Chrysostom and Fred Floyd have streets named in their honor.

Enough of the history lesson and back to the canon, I swam through the Blue Hole looking for lead fishing sinkers as the area is very popular with fishermen but could not find any, there was too much sand covering the underlying reef. I had a look for the ever present Tarwine, Herring and Tailor and found them no problem. The Tailor were where they always are just under the white water and the Herring were just a bit further out, the Tarwine they were on the gravel bottom in the surf zone looking for anything the surf churned up. I dived the back of the reef and checked all the exposed rock and came across an old rusty knife and then the small brass canon whilst trying to film Tarwine. It is only a small ornamental thing not a real canon, I whish I had found a real one though.

This find got me thinking, how the hell did the cannon end up where it was? I have found some pretty weird stuff under water over the years. Ranging from a sawn up firearm that the police were most interested in as the serial numbers were still readable and it wasn't even rusty yet, to hundreds of women's Panties and Bra's littering the bottom. Yes that was odd indeed, for now I will just add the canon to the collection of salvaged items that adorns a section of my display cabinet. 

Here is a picture of the canon on the beach and a video clip of where I found the canon have a look and tell me what is the weirdest thing you have found diving?