Shareware: You can try this program, but this version has some limited features or time usage restrictions. You should purchase it in order to remove those limits.
EarthNC Marine Charts w/seamless charts, user waypoints, and realtime navigation
EarthNC Marine Charts features seamless NOAA marine charts for US waters, user waypoints, and realtime navigation.
This app includes ads and restricts downloads to 50 tiles at a time - download Marine Charts pro to cache up to 10,000 tiles per download and remove the ads.System Requirements:No special requirements