They’re under pressure. Scientists have difficulty studying the Mariana trench, the deepest waters in the world, where human divers can’t explore. But cameras and traps have revealed a new species that swims more than 26,000 feet below the surface: the Mariana snailfish. Scaleless and translucent, the two-inch snailfish must withstand the darkness and extreme pressure of the ocean’s hadopelagic zone — but with few predators and many tiny crustaceans to eat, they appear to be thriving. Marine biologists say the find is a peek into virtually uncharted waters.