It was from Radio Shack. Outdoor unit was a bulb on a wire. Had a bracket for the indoor unit down below, and the bulb and wire lived in the locker behind. Prior to swim call, the unit came out of the bracket and the bulb would go over the side for a check on water temp at surface and 6' depth. Unfortunately the unit died (bad LCD) and I haven't seen a similar unit lately - they all seem to be wireless (which I'm hesitant to try in the water).