Has the world hydrography service been retired in ArcGIS Online. I have been getting the service is not available error message for a few days. I am logged into an organizational account, just in case it has become a premium service. Thanks to anyone who can solve the mystery.
I think I found the answer. From within the search for maps--the URL has an https and therefore generates the it can't be loaded error.
This url works http://hydrology.esri.com/arcgis/rest/services/WorldHydroReferenceOverlay/MapServer
when added to the add layer from web. Must be a glitch when the file was updated in February 16.,