[mario147]

Downloading previously purchased & downloaded apps

When you download a paid or free app on Google Play, the app isconnected to your Google Account, meaning that you get severalbenefits:
•If you get a new device, remove an app to free up space, or reset yourdevice, you can reinstall the app without purchasing it again.
•If you have multiple devices, you can install the app on all of your deviceswithout purchasing the app again.
•You can quickly find free or paidapps that you previously downloaded.

O sea, mas o menos lo que te dice jomogar.

Yo creo que la mejor opcion es la tercera, usar una tablet vieja (Navionics no necesita mucho) y dejarla en el barco con una buena funda por si se moja.