He seems to have all oceans as his patrol / assigned area. Other supes have territory based on their powers and a region's needs, and we know there are multiple Speedsters, for example. So, it stands to logic anyone else with Deep's powers would work closely with him. I've never heard of any, so I wondered, are there?
Ignoring the engineering challenges of constructing the structure or the structure withstanding the pressure.
If I sunk a large dome to the bottom of the ocean (standard sea floor is fine, don't need the deepest part) and sucked the water out, how much atmospheric pressure would remain in the air bubble dome?
Edit 2: it sounds like there are reasons not to do this other than just material strength concerns.
If I want my secret base to stay secret, we need to be at depth where light doesn't go. That also means it's cold. The issue with material strength is simple thickness and the increase in cost grows exponentially as the structure increases in size as well. The air becomes thick and unbreathable to the point of toxicity, so different mixes come into play. Then, because the different mixes do different things to humans, we also need to watch residents for signs of psychosis. Pressure on humans becomes toxic after about 3atm of pressure, and the seafloor can give us hundreds of atmospheres of pressure, so simply balancing the pressure inside to outside won't cut it.
Thanks to everyone who contributed calculus!!
Edit 1: NOW WE'RE COOKING! Follow-up questions:
1.) If I wanted a mad scientist lair at the ocean bottom, I'd just need to balance the pressures so the interior was livable for humans? Or keep the rating where "crush depth" is lower than wherever the lair is?
2.) At what upper limit, given acclimation, is pressure at depth lethal long-term to humans? Assuming I wanted to give wiggle room for structural integrity at near the upper limit where humans can comfortably endure the pressure.
3.) If I replaced the water with standard breathing mixture at 1.5 atmospheres in a shallow-ish tropical region, a dome the size of the Vegas sphere, what would be the target for structural integrity?
4.) Given the answer for #3, do we have material or technology at that rating currently for a dome the size of the Vegas sphere?