Thats really funny. My bullfrog has a habit of diving underwater when he's tired of getting looked at, and emitting a "jugorum" sound while submerging so that the tail end of the sound is a gargle of bubbles underwater. He'll eat crix from your hand for awhile and then suddenly realize what he is doing, and leap into the water emitting said sound. That's Luna for ya. Gotta love those bullfrogs!