You can look at the lakes from your home on the GPS but if you are in the garage you probably are not getting a signal from the satellite. Once the unit locks on to a signal you can zoom out to find your lake and zoom in to view it. At one time I could go to the HB website, look at a lake on the site, add waypoints or info and download to an SD chip and transfer to the DF and also transfer any info from my DF to the map on the website. Apparently they have discontinued that feature because I can't do it anymore.
I do not believe there is any way to put the Navionics chip in your PC and read it, but you can go to the Navionics site and pull up maps of your lakes. You can't input data to the Navionics chip except to do upgrades to it as they are released by Navionics.
At least that is my understanding.

Here is a link to the web app. http://www.navionics.com/en/webapp