What is this bubble popping up at the bottom of my screen?

[Karen LaRoche]

I have a Galaxy 6. I recently noticed this bubble popping up from bottom of my screen; it stays there for a second or two then disappears then another bubble comes up a minute or so later. It doesn't happen all the time though but if I am listening to my Bluetooth when it happens the sound fades out when the bubble appears. It also kind of looks like a wave of water in a circular shape.

 

[SpookDroid]

Is it a screenshot (or having a screenshot of what it looks like would help)? Or maybe Google Now/Assistant activating itself with perhaps the 'OK Google' command?