my local 48 acre lake has these in it. and i dont know what they do. what do they do and do they have any benefits as far as keeping fish near by. its the sprinkler thing in the back round

i think they add oxygen to the water

Not too sure what your talkin bout The round thing in the back?

i think they add oxygen to the water

We have them here up north.

They serve a few purposes. They keep the water moving so it doesn't get stagnant, they oxygenate the water, and up here they keep the water from freezing! Fishing around them can be productive due to added oxygen and surface movement.

Those are used in shallower bodies of water with mucky type bottoms to help oxygenate the water. Without them the amount of decomposing, organic matter on the bottom could lead to excessive CO2 problems and ultimately fish kills.

In warmer months they're a great place to search out fish.  Smaller baitfish will congregate around the oxygenated water and the bigger fish will follow.