From the Marvel press release:
Sub-Mariner Defends Atlantis In An All New Marvel Knights Series!
Namor has protected Atlantis from intruders for decades, but when a new group of explorers descend upon his city, can he protect it from mankind? Sub- Mariner: The Depths, will take you on a journey to the unpredictable depths of the sea. This is an Atlantis like you’ve never seen before! Fan favorite scribe Peter Milligan teams with acclaimed artist Esad Ribic, producing an all-new limited series that have you begging for more! Following in the tradition of the sold-out Spider-Man: Reign, Silver Surfer: Requiem and Logan, you can’t afford to miss this stunning new look at one of Marvel’s most enduring heroes!
Randolph Stein is a hero amongst men, a legendary adventurer with a thirst for the unknown that even the seven seas can not quench. There is a reason nobody has seen the fabled underwater city. A certain wing-heeled protector of the abyss will make sure that no secrets make it back to land, or will he? Prepare to strap yourselves in and take the plunge and experience a Sub-Mariner story like you’ve never before in Sub-Mariner: The Depths!
Collected in Sub-Mariner: The Depths.