Even with the 210 khz you will only be seeing a few inches of the bottom in water that shallow. With a standard 200 khz transducer you will only see about 1/3 of the depth, for example if the water is 15’ deep your cone will be approximately 5’ wide. If you want to get specific here is the geometric formula:
C=2xDepthxTangent(khz #/2)