Beratna

I’ve been seeing small 3-5 ft diameter circles of water that are smoother than the other surface water near my fishing spot. They don’t last long, maybe a few minutes. I’ve googled several times but can’t find a good answer. Are these fish swimming around under the surface causing a disturbance? Or some sort of under water current? I’ve tried casting out to those spots with some top water plugs/poppers but I haven’t gotten any bites. thanks in advance from a newbie angler