Trust me my son has found it a couple times. The one time I needed to use it I didn't. Some drunk lady bumped into my sailboat with her power boat as we were leaving the marina, she was right there, we were screaming at her, and she was oblivious. Crazy. She had to have been on pills or something. People on the other forum berated me for not using my horn. Only time I ever called 911 on another boater. She had a kid with her and was obviously wasted. 911 wanted me to come back in and file the report, I was like fuck that, I'm sailing and drinking beer. Now I keep my trusty horn in my cockpit.
No a human, and I don't believe an air horn would've saved her.