Most fish finders have particular depth ranges for their sonar. Once you exceed those ranges, the sonar beam cannot come back to the transducer so you will get wild readings (you will know it too). Side Imaging focuses more on extremely large coverage at a shallower depth so it may not give the desired results. But then again, 2D sonar is there for the deeper waters. But if you insist, you can upgrade your transducers for better coverage too.