Navionics has a Web App on their web site. It has all the current map data and is updated daily.
You view the maps on their website but it is not downloadable.
Go to the website, click on Products and then select Web App.
There are two layers of the Web App.
At the lower left of the panel is a round disc. If the disc is Grey, that is Navionics data.
If you click on the disc when at the 1000' zoom range or closer, it will turn Blue and that is the user generated contour lines of the Sonar Charts program.
They also have Navionics Mobile to download to a smart phone or tablet. Check you device's app purchasing feature.