SparkNotes: The War at Sea - World War I 1914-1918: A really good study guide for this topic.
World War I Naval Combat: A great collection of information on battles, warship losses, warship listings with full descriptions.
Naval Warfare and World War I (History Learning Site): This site includes biographies of the three leading British Admirals, the Battle of Jutland, British submarines and unrestricted submarine warfare.
SUBMARINE WAR
Q-BOATS
LUSITANIA