Sinking Chlorine Dispenser | Sunken Treasure | Sinks - Sanitizes Pool Water - Floats Up for Refilling | Uses LESS Chlorine (Dark Blue) USE LESS CHLORINE: Uses half the chlorine of a floating dispenser. Quickly pays for itself in reduced chlorine consumption. FLOATS WHEN EMPTY: It floats to the surface when it needs refilling. No more wondering if you are out of chlorine. And your dog will leave it alone since it is underwater. STOP BREATHING FUMES: The chlorine tab is always submerged, dissolving all the chlorine into the water from the bottom up. So you arent wasting the chlorine into the air (like with floating chlorine dispensers) and there are no harmful chlorine vapors to breathe. DURABLE: Stays underwater, so its not getting scorched by the sun. Stop buying the cheap ones and replacing every season. Award winning patented design. Not recommended for vinyl lined pools.