Do I have a leak or something else wrong?

[Andybme]

Thank you for the detailed reply but I have neither a heater nor a chemical feeder. As for SWCG not sure what that is.

Interesting video.

What is displayed is simply clear water with a different refractive index than the rest of the pool water. I can think of at least three possible reasons:
1. You have a heater, and it is firing.
2. You have some sort of chemical feeder active.
3. You have a SWCG that is operating.

A leak means water is leaving your pool. Unless you are losing water, you don't have a leak.