I wonder if the bottom of the ocean would be a good place for a datacenter, networked directly to those cables. There would be ample opportunities for power generation and cooling.
I'm not sure about underwater, but one way to save lots of money on a datacenter would be to build it on the shore next to a deep body of water and a massive bandwidth supply. That way you can chill the datacenter using Lake Source Cooling, which cuts power consumption by ~80%. If you're ever in Ithaca there is a huge LSC plant on Cayuga Lake that's insanely cool to walk around in.
An enclosed structure located where you're describing would be under incredible pressure from the water above, unless it's close to the surface. Also you would need people to man it. They wouldn't last long without sunlight. Finally, hard drives, switches, and other items fail all the time. You would need a storage area for food, water, shelter, and replacement gadgets, as well as toilets of some type.
Do you know if the environment would put undue wear and tear on the equipment housing? I don't know much about undersea material constraints. Otherwise, that's an interesting idea. One of my favorite books as a kid was about scientists who lived under the sea.
