Most importantly if the water table of the surrounding soil is high enough, it will lift an empty pool, even concrete. At most you would lower the water level below the lights. You’re likely getting wet either way.

In this case great minds (you and I) think alike.

interesting idea. I will try that one next time

Easy, it’s cheaper to pay the electrician to use his SCUBA gear than it is to drain and fill a pool with water.