Warlock Patron: The Leviathan

From the introduction: A creature older than any who have walked on land, that knows every mystery and artifact below the waves, the Leviathan calls to those who would wield the power of the sea, and grants the might of a raging storm. This subclass offers variety of elemental abilities, increasing your capabilities underwater, while enhancing your control effects on enemies. It also offers options for Pacts and more invocations.