The sea to the north is characterized by slow currents and weak, changeable winds. Ships can become stranded for such long periods that cannibalism is common among ill-prepared vessels. It's called the Swabbie Sea because the poor bastard who swabs the deck usually gets eaten first.
The warships of Orisaarland are powered by Hadrus as well as manpower, giving them the necessary speed to combat piracy in the becalmed sea.