Forbes had attracted many supporters. Still, even those who might allow for some primitive or ancient life in the depths could not imagine the true extent of life there.

Forbes went on to have a distinguished career as a curator and paleontologist at the Museum of the Geological Society of London. He was also professor of botany at King’s College, London, and professor of natural history at the Royal School of Mines and the University of Edinburgh, where he worked on his book Natural History of European Seas, one of the first general studies of oceanography. Unfortunately, Forbes died in 1854 at the age of 39. His book, which included the azoic-zone idea, was published five years after his death—the same year Darwin published On the Origin of Species. Had Forbes lived a little longer, he would have seen his theory soundly quashed by Sir Charles Wyville Thomson, whose expeditions on the HMS Porcupine (1869) and the HMS Challenger (1872–76) changed the idea of what could live in the depths. Thomson even managed a sounding in the Mariana Trench. Yet Forbes stimulated interest in deep-sea research, and his zones foreshadowed later work and understanding of the biogeography of the sea.

Even in Forbes’ lifetime, various accounts hinted at life below his self-imposed 1,800 feet (550 m). And despite Thomson’s work, many still thought that specimens pulled up from the deep had died in surface waters, sunk down and become entombed, beyond the reach of decay. The number of species found at great depth at that time would seem to argue against this. But facts traveled slowly in those days, and in the absence of personal experience or overwhelming proof, people believed what they wanted to believe. Hailing from a leading center of scholarship, Forbes had attracted many supporters. Still, even those who might allow for some primitive or ancient life in the depths could not imagine the true extent of life there. Yes, many deep areas are anoxic, or oxygen-poor, but despite the lack of light, the persistently cold (though not frozen) water and the extreme pressure, the sea is filled with life.

Suppose we could sit in a boat and lower a cable carrying the latest iPhone mounted within a spherical underwater housing. The iPhone’s video camera would be capable of panning a full 360 degrees, with lights to illuminate the subject and fill in the shadows. Our camera is imaginary, but the idea of it is not far-fetched. Low-budget marine researchers use “pole cams”—underwater cameras mounted on long poles—to film below the surface. To document the Census of Marine Life in its film Oceans, Galatée Films worked in 50 locations around the world, towing a torpedo camera that jetted along with swimmers at 15 knots. Of course, the intense pressures of the deep layers present a challenge to sampling at depth, but the technology exists. The hypothetical expedition described below offers one example of a long trip to the ocean bottom, although we should always keep in mind that no two journeys would ever be the same.

Let’s call our imagined camera the “iMonstercam.” If our iMonstercam could descend to the bottom foot by foot, layer by layer, what would it see? We could bait the device to guarantee some action, as National Geographic or television producers on a deadline might do, but that would prejudice our search toward bloodthirsty predators. Let’s try for a truer picture. Our iMonstercam attachments might include a hydrophone, or underwater microphone, to hear and record what’s going on in the sea. There would also be a tiny acoustic Doppler sensor to gauge the speed and direction of the currents, as well as sensors for measuring water conductivity, temperature and depth.