The US Geological Survey has been around forever.  Long before there were tools like Google Earth and Google Maps, there were topographic survey maps published by the USGS, and these data are still essential.

Increasingly, USGS has seen its role to provide quality data to the GIS community, and increasingly you can find it in KML form.  Two KMLs recently became available for what are truly useful datasets for fishermen:  the National Hydrology Dataset ("NHD") and the National Geographics Names Dataset ("Geonames").  Both are available for download in the Data Resources menu in the sidebar.

Just how useful is illustrated by 3 screen shots.  These happen to be a small segment of the "High Peaks" region of NY's Adirondack.  The sources of the Hudson River and the Ausable Rivers are in the shot below.  "Really?", you might ask.  Because unfortunately the stock aerial imagery in Google Earth doesn't show water resources very clearly.

Now check out the same area, with the NHD dataset turned on.

Now you can see all of the resources we care about as fisherman clearly marked.

Essential as it is, you need to use this dataset carefully.  Virtually every water feature down to and including drainage ditches is in this system, so it's an absolutely massive database.  The KML links you to the NHD servers, and draws down information as it needs it based on the extent you're viewing.  Change your view and the data needs updating.  Due to the size of the DB and the number of features in every view, It updates slowly (wait... yes it's coming).  You don't want to turn it on when you're not zoomed in, or labels and lines will totally clutter your screen.  We've noticed in recent months that the USGS has been working to improve the behavior of the KML.  All of these comments still apply, but it's a bit better than it used to be even a few weeks ago.  At high resolution, too, the NHD now marks flow direction, and features like springs and wells.

The Geonames database is a "nice to have" out East, and nearly essential out West.  Below, see the same view with NHD turned off and Geonames on.  Note you still get the water feature names (though not as nicely oriented as in NHD), but now you see the names of the mountains and other features.  Out West, many smaller streams aren't named in the NHD database, but are named after the canyon through which they run.  So "Toro Canyon Creek" will be the unnamed stream running through "Toro Canyon", which you'll find on Geonames (and probably will need to locate in the first instance using the search function in in the National Map)