If it were possible, wouldn't it be a perpetual motion machine?
This is not feasible. Even if it does not use part of the electrical energy for lighting, it is not feasible to reinject all the electrical energy into the pool.
The first. The explanation is the law of conservation of energy. The energy will not decrease even if it increases. It will only change from one energy to another.
Second explanation, if you don't understand the law of conservation of energy, let's calculate that the water in a large swimming pool located at a height has potential energy. Can a generator convert all potential energy into potential energy. water into electrical energy? The answer is no. Ordinary generators only have 90%. Even if you want to reach this number, just think of it as 90%. Then you use electrical power to pump the water into the pool. Electricity pumps the water. Converttie in potential energy, there is also a loss on the motor, and the overall loss is 10%. If you do the math, when you drain the water from the pool and then pump it out, the water that is in the pool is 10%. The swimming pool will only represent 81% of the original volume, not to mention the lighting? After a few laps, there will be no more water in your pool. Of course, in reality, in the first round, it's fine if your pool water is 50% of the original water.
So, don't do it fancy. Perpetual motion machine,