Lowrance M68C GPS Receiver "reading bottom high speeds" Questions

...reading bottom I have a transume mounted 50/200 kh transducer. When the 200 kh is reading the bottom fine even at high speed. The 50kh even in shallow water is not reading the bottom very well in ...

...bottom, although they are prone to this problem. The way the sonic waves have to travel through the water is affected by turbulence, especially by air bubbles and cavitation, and by the transducer ...