Unfortunately, you can’t guarantee a good connection on the water. With the Nautical Maps app, you can download the maps to your device so you’re not caught out in dead spots.
After installing the app, a pop-up in the map view will ask if you want to download the maps.
You can also find this option in your ‘Profile’ (on the bottom right-hand side in the menu bar). Select ‘Download maps’ from the ‘Maps’ list to save them to your device.