Wrath & Glory: Warhammer 40000 Roleplay Dark Tides Adventure - Rules of Play says:
he ocean world of Charybdion seethes with discontent and a growing sense of danger. Dark Tides is an anthology of five linked adventures that bring your heroes face-to-face with the dangerous villains responsible for Charybdion’s troubles. Can your heroes confront the vile forces spreading insanity and corruption?