I'd like to achieve 4.5 foot depth underwater. I thought a BT module or WIFI board would work fine sealed in a submarine. Radio communication reflects off water? Also, what if I heat shrink-wrap an ultrasonic ping sensor, mount it on top the hull and use it for obstacle avoidance? Will the chirp and echo work underwater?
so I don't understand why I'm asked how much horizontal I'm aiming for
Maybe the best idea would be to have a submarine with tube and a float where the BT module would be placed. I'll run the BT module's wires down the tube to the submarine. That way it can be BT radio controlled and still be a stealthy spy bot.