Deep Domain (Star Trek: The Original Series, #33)

A routine diplomatic visit to the water-world of Akkalla becomes a nightmarish search for a missing Spock and Chekov, a search that plunges Admiral Kirk headlong into a corrupt government's desperate struggle to retain power. For both A Federation Science outpost and Akkalla's valiant freedom fighters have begun uncovering the ancient secrets hidden beneath her tranquil oceans. Secrets whose exposure may even mean civil war for the people of Akkalla -- and death for the crew of the Starship Enterprise™.