I've read about this a couple of times. My first thought would be that a passenger/tour boat should have redundant warning signals. The air horn didn't work, but why no flares or even a hand held air horn. Seems someone needs to re-think the safety devices, making sure there are redundant warning systems available, especially if the boat is shut down. Some type of manual warning system, not dependent on the boat's systems should be required.
AFC 17' 2+2 (sold in 2012)
Sunfish project boat
Sailing a large boat on a small lake is very tacky.