Safety Turtle Child Immersion Alarm Kit - Blue Safety Turtle works with ALL Fresh Water, natural [lake, river and pond] or man made [pool, hot tub and pond]. A loud alarm instantly sounds at the Base Station when the Turtle is immersed in water. The alarm continues to sound until it is reset The Safety Turtle system can be progressively expanded through the purchase of additional sensors(s) of the same color The Immersion Alarm may also be used in conjunction with the Wireless Gate Alarm which helps enhance the security of a safety fence The Turtle has a battery life of 3 - 4 years. Base station battery pack sold separately