Starfish by Peter Watts
In a future overpopulated and under-resourced Earth, a geothermal energy plant has been constructed in a trench thousands of miles under the Pacific Ocean’s surface. The humans of the maintenance crew who live and work in and around the power station have been genetically engineered to withstand the harsh deep-sea environment. But the only people who are willing to undergo this biological manipulation and unpleasant living situation are outcasts, misfits, the psychologically damaged, and criminals.
We meet them aboard the Beebe station where they live together in a cramped environment that can be tense,