Unlike the Imperial Army, the Imperial Navy maintains an active standing force.
This is presumably also under the jurisdiction of the Warlord, likely working in conjunction with high-ranking members of the House of Orca, whose members make up the majority of the Navy.
The Navy is responsible for protecting shipping routes between the Empire and places like Elde Island and Greenaere, as well as trade routes with the Eastern Kingdoms.
Most Orca are expected to serve in the Navy for a certain portion of the year as a duty to their house. Presumably, the Empire in turn grants the house of Orca special privileges in return for this service.
In times of war, the Navy may employ Press Gangs to conscript additional Teckla or Easterners into their wartime forces.
The standard fighting ship of the Imperial Navy is the "Man-o-War".