put a gopro or underwater camera in and leave it for an hour - pull it out and you will most likely see waves of plankton plowing in the water column, and you will see them swimming in front of the lens as well.
Fast forward to about 4:30 in this video and you will see the little whitish specs in front of the camera - those are zooplankton and little giblets of minnow food swimming around.
in this still cam video you can see the light reflecting off them as they float by the camera - it's not silt. The odd time you can see them propelling themselves.
