In-Situ Sondes collect the horizontal movement in specified directions (North, South, East, West) and vertical In-Situ Sondes collect the upwelling and settling of water column particulate motion.

These specially designed Sondes produce movement of fluid mud and dense particle movements in a maximum of 6 directions. The resulting data are reported in terms of the mass movement or motion  (mass/unit area/time - kg/meter²/day) of the dense nephelometry layer at or near the water bottom in aquatic habitats.

Horizontal motion measurements in Indian River Lagoon areas suggest the equivalent of a 10 lb bag of flour of fluid mud horizontally moving per meter² in a day - or well over a ton of fluid mud moving per year per meter².

Obviously, this fluid mud blocks light from reaching the bottom of the water column where aquatic vegetation and other organisms use the light for growth and to support living functions such as "seeing their food".