The Eternal Tide

From the Introduction:

The Eternal Tide takes the Acolytes to the ocean world of Spectoris, home of the infamous Magos Genetus Halix Redole. A heretic with shadowy connections to their own Inquisitor has stolen documents penned by Redole, and appears to be on the trail of greater forbidden knowledge. The Acolytes will have to explore the forgotten depths of the ocean, brave the unfamiliar territory of the open sea, and tangle with savage criminals in order to track their quarry. They may also find themselves faced with some deep questions of what they desire, and who they can trust.