The Abecean Sea is a body of water to the west of Tamriel that sits between Cyrodiil, Hammerfell, Valenwood, and Summerset Isle. The sea is encompassed by the Eltheric Ocean.
In Stirk, the Abecean Sea separates the island of Stirk from Anvil and the rest of mainland Cyrodiil. In the waters near Stirk lies the shipwreck of the Kintyra II, which you will learn about in the quest The Ballad of Jean and Mori and explore during the quest The Lost Delivery.