The map has disappeared ...
The advantage of this approach is that the same maps and storage are shared by all apps using mapping so you're quite likely to already have the maps downloaded.
The downside - as I'm well aware - is that at sea you're not going to be using maps in other apps and if you don't have a cached map or an internet connection then you've nothing. So at least a simple offline map has been on my development plans for sometime although I can't yet promise a timescale.