Raymarine depth randomly cycles down to 0 and back up again

[hikersailor]

My TriData instrument failed so I replaced it with a dedicated depth instrument that will on occasion especially in shallow water about 10' start showing erroneous depth reading as it cycles up or down as much as 100' with an arrow showing the trending depth displayed on the right side. Called Raymarine with little result. This happens when I need it most in shallow water which is just great. Very erratic and does it when it feels like it.

[SaltyMetals]

I get this problem when there is a lot of suspended silt in the water. Usually at a river estuary. Very frustrating bec that is exactly when you need it to get over/around a bar or navigate a narrow, winding channel. My sensor is a Raymarine unit from 2004 with a TriData ST60 display. No idea what frequency it runs on or whether that can even be changed. Apart from the silt problem it has served me very well.

[hikersailor]

Salty Metals thanks for the input. Interesting to see that suspended material in water i.e. silt might cause the disfunction.