We are using this for our swimming pool. Another kind of these we had bought previously for the pool, although cheaper, per square foot, falls apart in about a year. These have lasted a couple years now and show no sign of deterioration. So we have 8 or so of these in our pool, having moved slowly toward them as the other type deteriorates. We also have a temperature monitoring system (Tempurity) that records the temperature of the pool constantly. So we have historical records for more than a year. I can't actually say that the temperature of the pool is better when these are in although you can feel warm water underneath - but I think it is just blocking the rays from hitting deeper in the pool. Where it does seem to work well is in reducing evaporation. Here in California water is expensive and that is a big benefit. They are relatively easy to get all 8 out of the water when you want to swim. But they are much easier to get out and back in when you are in the pool. It is more difficult from the edge.