I haven't kept up with Bounty Hunter so you should check your specific model but most detectors today have a waterproof coil. This means you can submerge the detector up to the level of the control box. Be careful though because unless the detector is advertised specifically as being for underwater use the control box will not be waterproof. Getting the control box wet may fry the electronics inside. This includes using it in the rain. Another thing to remember is to never put the coil underwater and then raise it higher than the control box. When submerged water gets into the shaft and if tilted the water can run up the shaft and may get to the electronics.
Oh, and the only dumb question is the one you don't ask and get in trouble because of it.
Bounty Hunters can have their coils submerged (not the boxes!) but there have been reported problems of water leaking into the coil. If I was you, I'd take some heavy duty glue like this stuff and coat the coil wire connector in it to seal it off from dirt and water leakage. After that, I'd say go for it as long as you keep the box dry.
This is the stuff I put on my Tracker IV's coil connection.