Freshwater bait ball from the surface? Or Ogopogo?

[AngloFish]

Very cool little vid of what we are assuming was a bait ball (minnows??). We had just finished the day out and were discussing it when a whirl pool about 2ft in diameter erupted about 20ft from one of the divers in the water.
It maintained itself while traveling across nearly the entire length of the lake.
I'm guessing this is how lake monster rumors get started
Anyone have any idea of what freshwater lake fish that do this sort of thing?

 

[Kharon]

I would make a WAG that it's a bait ball being chased and consumed by bigger fish - maybe smallmouth bass OR a spawning ball of minnows or even some larger fish.

By the way, a WAG is a wild a$$ed guess.