Dynamic shadows fading out differently on translucent materials than opaque surfaces...

In the attached image the bright blueish ribbons along the beaches is an overlayed geometry with translucent material to make smooth transition between water and sand. Unfortunatly the dynamic shadows fade out in the distance (see how they remain visible with nice resolution on the water or the sand (both opaque materials)). When getting close (second image), the shadows appear, though. Is there a way to improve this?
Thanks a lot!