Look up images of drained canals in the uk for a general idea of what the canal bed looks like and the slope angle

Someone said many people fall in and drown despite the shallowness because the slope plus the slippery silt makes it impossible or nearly impossible to stand up. how slippery is the silt exactly? and the image of the drained canal is just a reference to get an idea of the canal bed, the scenario would involve a canal thats full not drained