I would have suggested the NOAA website, but their online viewer requires Flash, support for which has been/is being dropped in Android. There are workarounds, but probably not worth the effort.
NOAA's On-Line Chart Viewer
Otherwise, there are a number of Android apps that can be downloaded that pull from the free NOAA chart database, so all you are out is the cost of the app (NOAA provides US charts
online for free, free online coverage for the rest of the world varies depending on which country/charting agency). I've used this one on other Android devices, but not on the Kindle:
Android | EarthNC
It has some drawbacks as a navigation
package (or maybe my device did), but if all you want is a chart viewer...
Or you can search around on CF for OpenCpn
on Android, I know it's been done.