I don't know if you knew this, but Australia has had three Prime Ministers who died in office. Two of them died of natural causes, while the third one we can only assume died, as he went swimming one day in the sea and never came back.
Now sure, we're a small nation, not super important, so I suppose it makes sense that we've not had any assassinations, compared to other nations.
Or, you know, maybe our assassins are just a little better at making it look like natural causes.
Well, mostly. I wouldn't begrudge an aquatic shortcut if needed.