Cruising/sailing with musical instruments... ?
Well, I guess I'll have to forget about my 4 valve contra tuba. I spent all winter making a harness so I can strap the instrument into the dingy. Also had the bell made so it screws on and off to save space. The nice thing about the tuba is the pipe is wide enough to use as storage.
I think a Bosun whistle may make the most sense. Although a plastic uke may be okay.
Still thinking about ideas. I won't consider the Oboe. If ya want to be a good musician ya have to know your bass from your oboe.