signaling devices, boat to divers
 

Does anyone know of a good setup to use as a signalling ( sounding)
device to underwater divers?
I was considering a horn mounted to the inside hull bottom.
Would like to be able to alert divers to stay clear of the boat in
case the engine had to be started while divers are down or to warn of
other boats approaching the dive area..etc.
Thanks for any advice.
John C.