I'm a relatively new pool owner, and I'm fighting a leak somewhere in the pool. I had a local pool company use a device to scan the pool for leaks, and the device detected nothing. I changed the gaskets on the returns and the skimmer boxes, and the problem has worsened slightly. I want to add some silicone where appropriate. To do so, I'd like to vacate the water around the particular return as I service it. I've attached a photo of a device that I viewed in an online video. What is the device called?