Good post. I last used sound signals on Nov. 12/06, when we entered Toronto Harbour to fuel up for winter layup. The visibility was about fifty feet in the fog, and I had my wife at the bow on lookout for the buoys and I was at the poop deck wheel giving the five short blasts. At that time of year, the only real danger was the ferries to the Island, but as Toronto Harbour is frequently jammed with everything from tall ships to canoes and Zodiacs, they are on their game. I kept a VHF "watch" on ch. 13 and 16 and, prior to leaving, plotted my turns via the harbour buoys using a paper chart and standard compass bearings, plus keeping a constant speed of 4 knots so I could figure out roughly the intervals between buoys/course changes.
It was hardly a major feat of navigational excellence, particularly as I could frequently see the shore, more or less, but we found the fuel dock on the Island without incident, and got back to our own club in a similarly uneventful manner. Other than finding a harbour entrance during a power blackout (the buoys were working, but the red and green on the seawall weren't!), that is about as complex as it gets on Lake Ontario...
The only thing of note that happened was I heard a ferry captain on 13 telling his counterpart that "some guy's out there in a yacht giving five blasts...you don't get that much around here". Presumably they had us on radar as I don't recall seeing or hearing a ferry, despite crossing their lanes.