These Hydor submersible water heaters are completely submersible, UL approved, salt water compatible and shatterproof. Instead of the typical metal element in a breakable glass tube, these heaters utilize a polymer sheet that uniformly heats a shatterproof glass tube. The temperature is controlled and maintained by a highly precise micro-switch controller, adjustable from 70° to 89ºF. Heaters are 115V/60 Hz with a 6’ cord. One-year warranty.