From a post on ENWorld (why I almost missed it)
Aquatic Depths & Denizens is ready for playtest release!
This PSR PDF focuses on adventuring underwater. It includes rules for swimming, drowning, fighting and spellcasting under the waves, five player character aquatic races, an assortment of aquatic spells, and a plethora of marine monsters. Download your copy and playtest today.
Of course, helpful folks who playtest the PDF and/or provide feedback receive credit in the final PDF. They also receive a free copy of the final PDF, providing I have an e-mail address. To further sweeten the incentives, playtesters/feedbackers may also select any single PDF from my on-line catalog to receive for free (again providing I have an e-mail address). My email address is mark at spesmagna dot com.