sorry, should have been more informative the first time.
it's provided by NOAA, my favorite taxpayer supported government
agency, and is absolutely free. just look it up on the google
play store and download it.
it has a menu which allows you to install charts
and/or coast pilots from all of the regions around the usa and offshore
, one region at a time. it will use the gps
facility on your tablet to track you across the charts.
i haven't had time yet to really play with it but if all you ever use it for is just to view charts it's worth the cost - which is zero.
i tried to download it to my samsung galaxy adnroid phone
but google play store wouldn't allow that. apparently it's only available at the tablet level for now.