Deep Terror — Eric S. Brown

At the bottom of the ocean lies deep terror!The former research station Pioneer 4 has been converted into a facility for harvesting and extracting the bio-matter needed to create a lifespan increasing drug. Those aboard the station find themselves far from alone, almost constantly under attack by monsters from the nearby oceanic trench, as their chief security officer goes on an insane, mass killing spree. His replacement, Marshal McShane, is going to have his hands full dealing not only with the aftermath of that horror but a brand new evil, seeping out of the darkness of the trench that threatens everyone inside of Pioneer 4.