I’ve had a lifetime love affair with the underwater world. Influenced by everything from Jacques Cousteau films and TV specials to the ancient Sea Hunt TV show with Lloyd Bridges, I’ve spent a lot of my swimming time under the surface—on purpose! As a pre-teen I made my own “underwater habitats”, anchoring plastic garbage pails to the bottom of our backyard swimming pool, and submerging overturned canoes in lakes. Naturally, I became a scuba diver as an adult, fascinated by shipwrecks and coral reefs—if you visit a tropical vacation spot and don’t spend time underwater on the reefs, you’re missing some jaw-dropping beauty that the above-water environment just can’t match.

I loved to read science fiction stories about the undersea world, too. There have never been that many. Except for the iconic Twenty Thousand Leagues Under the Sea by Jules Verne, The Deep Range by Arthur C. Clarke stands as the earliest major undersea SF work I can remember. Peter Watts’ Rifter series and Michael Crichton’s Sphere are standouts too. And yet, I’m convinced that our oceans will play an even bigger role in human life of the future than they do now.

From ancient times, oceans have provided essential transportation routes, and today the shipping and shipbuilding industries comprise nearly ten percent of the economic value added from the oceans worldwide, and about five percent of the employment, according to recent reports. Fishing (wild) and fish processing are the largest economic sectors (employing 36% of the workforce) but maritime and coastal tourism comes an impressive second (23% of employment). In terms of economic value, offshore gas and oil is extremely important. But I expect that this whole picture will be very different a hundred years from now.

Wild fish stocks have been devastated by overfishing, pollution, ocean acidification, and climate change. As the carbon dioxide in our atmosphere increases, ocean waters will become even more acidic (affecting the entire oceanic food chain), currents will shift, and fish populations will struggle to recover. If we want to continue to eat seafood, it will have to come from aquaculture. There are serious problems with fish farming that must be overcome, especially related to the spread of disease, and genetic threats from interbreeding. But it’s reasonable to expect that a century from now we’ll see giant aquaculture installations patrolled by submersibles (like Clarke imagined in The Deep Range). We might not raise whales for their meat, but certainly fish and crustaceans, and some years farther into the future we’ll have mammoth production facilities for edible forms of algae, like spirulina, drawing nutrient-rich water up from the ocean depths for the crops, while being self-sufficient in energy thanks to the water temperature differences (like geothermal sources we use today). The algae farming business will explode as soon as we develop food processing technologies that will turn the raw algae into more palatable forms of protein. Drop into a vegan food store sometime and see what can be done with vegetable-based fake meat.

I expect oil and gas production in the oceans to increase over the coming decades, but the environmental risks will eventually be more than we’re willing to stomach. Instead, energy production from offshore wind farms, ocean tide-powered turbines, and possibly the raw energy of ocean floor volcanic vents will all be developed into significant industries, as long as we’re careful to avoid degradation of the environment. I hope (and believe) that we’ll be wise enough to wean ourselves off fossil fuels, which will reduce some of the most hazardous ocean shipping. We also need to become less obsessed with consumer goods, or at least opt for more locally-produced foods and goods, out of concern for the environment (and plain good sense). So ocean shipping will decrease in the coming century or two, but it may be replaced by increased tourism, as populations in developed countries age (and flock to cruise ships and beach resorts) and the middle classes of developing countries become able to afford such luxuries.

Even if we do cut back on oil and gas extraction in the oceans, there’s every likelihood that we’ll go after other resources in the ocean floor as they become harder to get on land. But the environmental impact could be a nightmare, so my personal hope is that we’ll turn to the asteroids for our minerals and chemicals, and not to the seabed. A better alternative would be to develop more efficient ways of extracting minerals from seawater itself, especially since that could tie in with desalinization machinery, producing much-needed fresh water in an increasingly hot climate. After all, the water created by such efforts will return to the ocean as rain and river runoff, replenishing what is taken.

Will we ever have undersea colonies under vast transparent domes, like some pulp stories and comic books have portrayed? I hate to say it (because the geek in me will be heartbroken) but probably not. To live under the ocean full-time we will have to genetically alter our own bodies, either to cope with the side-effects of breathing high pressure air for long periods of time, or to actually enable us to ‘breathe’ water ourselves, like fish. I think genetic science will eventually be capable of both, but there will be no reason to do either on a large scale. Robotic machinery will be much more efficient at doing any task we need done in the underwater environment, and living underwater will never be a practical remedy for overcrowding the land surfaces of our planet. Giant floating islands, maybe, but not vast domed cities on the ocean floor.

Still, if you’re an underwater junkie, don’t despair. Where underwater cities may never be practical, a premium hotel industry on the seafloor might do just fine.