Free Romulus Buckle and the Luminiferous Aether (The Chronicles of the Pneumatic Zeppelin #3) by Richard Ellis Preston Jr.

LATIFUNDIUM
    Romulus Buckle, his head locked inside a copper diving helmet with windows of green glass, stepped out of the Dart ’s flooded airlock and dropped into the freezing squeeze of the ocean. It wasn’t much of a drop—five feet to the sandy bottom—and the uncomfortable heaviness of his suit was replaced by a pleasant sensation of buoyancy held in check by the bulk of his boots and weight belt. The oxygen tanks and helmet felt familiar, similar as they were to a zeppelineer’s high altitude and poison gas equipment, though they were bulkier and more rigid in their construction. He gripped two weapons: a long-handled underwater spear and a small crossbow harpoon with a firing mechanism which combined tension and compressed air.
    The Atlantis Approaches were a dangerous place, Felix had said. The Guardians, nasty creatures, operated in loose platoons under the command of vile beasties called ‘gagools’. Kill the gagools first if you can, Felix had said. Kill the gagools first and your odds of survival increase exponentially. One can beg an Atlantean sentinel or herder for one’s life but not a gagool.
    The tan-colored bottom reflected the morning light but it all felt melancholy, surely the effect of the greenish glass of his helmet windows deflecting much of the light. He was also still in the shadow of the Dart ’s belly. Bending as low as he could to clear the keel, he trudged out into the weak, undulating light, half-stumbling in slow motion as he learned how to move his boots over the bottom swells. It was humid inside his helmet and the faceplate trickled with condensation. The sounds of his breathing and the ping of the oxygen valves were oppressive but when he straightened up and saw the glorious green-blue-white play and sparkle of light and water on the surface he felt better.
    Buckle turned, slow and awkward, to join Sabrina, Welly, and Penny Dreadful, who were collecting under the guidance of Kishi. They looked like phantoms in a netherworld, faces ghoulish in the round green portals of their helmets, the interiors lit by tubes of bioluminescent boil. It was near impossible to tell who was inside each suit except for size. Penny Dreadful, wearing no gear of any kind, moved toward him, smoothly, half-gliding across the bottom, looking like it was at home. Its golden eyes had a buggish bulge to them, enlarged by translucent lenses which had dropped from the metal skull and sealed the sockets. The machine had transformed itself once it was in the water: a sheer metal webbing had unfolded from its hands and feet, turning them into flippers, and a shark-like dorsal fin now thrust up from a slot in its back.
    It took five more minutes for the remainder of the Dart ’s crew to descend from the airlock, with Marsh and Rachel carrying Gustey between them on a basket stretcher. The last man out was Captain Felix. Once his boots hit bottom, Felix was on the move, leaning forward as he drove his legs, his boots sending up punches of dislodged sand. He jabbed his gloved finger forward as he passed Buckle, his face looking compressed and angry inside his helmet.
    Buckle swung around and hauled his boots across the sand, staying close to Felix and Kishi as they took the lead and humped toward the towering domes of Atlantis. Buckle could see all seven of the domes, one large one surrounded by six more of varying sizes, and they all pulsed with a mysterious white light.
    Buckle tested the unfamiliar balance of the spear in his hand. Felix had warned them to keep moving at all times and not to get spread out, for on foot they were likely to encounter the Guardians. If there was no Atlantean sentinel present with the Guardians—and apparently there often wasn’t—there would be a sharp fight to make their way through. The group numbered ten souls—not counting Penny Dreadful— and they were all well armed.
    Atlantis loomed closer slowly, very slowly. Buckle leaned into his stride, throwing one heavy boot ahead