Milliard Pool Thermometer Sinking for Accurate Below Surface Readings with Pocket and String, for Outdoor/Indoor Swimming Pools, Hot Tub, Spa, Jacuzzi and Pond Our sinking thermometer measures temperature from below the waters surface for more accurate readings that arent affected by the suns rays above. Includes rope tether to keep the thermometer from floating away Made from durable ABS plastic to last from season to season No guesswork with our accurate temperature display Thermometer is 10 tall and reads in both F and C