What unit you have? If you have a Humminbird you can download Humviewer you can retrieve your recordings from your sonar and upload them to your computer and see them in Humviewer. You would be able to see MUCH more on the recording in your home on the big screen. You can then see and find and mark points and upload them back to your card and put back in your sonar for you to go check those spots.
The bigger the screen you have on your unit the better it is to see those hings you would miss on smaller screens. Trust me. I have found MANY places i did nit see on the screen when I was out but found them later after reviewing.
I think Lowrance has software as well but i am not familiar with it.
Don't give up on SI. It is the way of the future.
Good luck.