From PathfinderWiki

The Miasmere is the name given to the large bay in the Obari Ocean just off the coast of Nex, between the capital Quantium and Valkus Isle. It is very heavily polluted by the waste products of Quantium's magical industries. Its foul smell hangs over the streets of the city, and its acidic composition eats away at unprotected ships' hulls.

In times of war, Nex's spellcasters agitate the water and bring waves of the foul stuff down upon enemy ships. The resulting wreckage and corpses are added to the Miasmere's unsavoury flotsam.1