Water threslold

Hi every one,
i need to apply water threshold on sentinel 1 data . Then, the backscattering similarity between water and fine sand made a confusion in the results.the question is :
how i can Separates water from surrounding smooth surface???
My current workflow is Remove-thermal-Noise > Apply Orbit File >Calibrate to sigma0 >Speckle Filtering ->Linear To dB > Applying water threshold.
the second Q :
Can wet soils be determined using single sentinel 1 image?

if you have dual-polarization Sentinel-1 data you might check if there is a difference of the signature in both channels between water and smooth land surfaces. Create an RGB image using
red VV
green VH
blue VV/VH

and check if the colors are different for water and smooth surfaces. Maybe you need to define thresholds in both polarizations vial the band math, e.g.

IF VV < 0.5 AND VH < 0.05 THEN 1 ELSE 0

Also have a look at @SAR2016’s topics and posts who initiated various discussions on finding thresholds for water classification. https://forum.step.esa.int/u/sar2016/summary

thanks a lot sir