I think what you are referring to is called a lonely buoy, you hear it often in the film, "The cruel sea" when Compass Rose is entering, or leaving harbour......
Methinks you'd best start with a visit to Mssrs Babcock for the doings for about 500psi of superheated steam, and rig it up to a contraption that probably weighs a coupla tons...though I expect they were all scrapped four/five decades ago.
Or search the internet for an electronic version, which isn't easy to find.
I'm seriously thinking of fitting one of those on my boat for when we go up the River Wey - that'll make the bugger's heads turn, might even force those blasted narrow boats to move over. It will certainly cause consternation, they'll all be wondering where the noise came from and that appeals to all the males in my family's sense of humour. Thing is, what do I need for a speaker that will really make it heard? Do I need an additional amplifier?