That would depend on several things. For one, how dense that grid would be. For another, what would be built into/next to/adjacent to the nodes/hubs and spokes

That would depend on several things. For one, how dense that grid would be. For another, what would be built into/next to/adjacent to the nodes/hubs and spokes of that grid, making building such a grid of floating, submerged tunnels worthwile in the first place. Hen<->Egg, bootstrapping, yadda yarr yarr... edding: Also imagine something like really long freight trains, a mile or so, double stacked, only running at something like 200 mph. And compare the capacity with any freight plane in use, vs. the speed of container ships. Also the possibility for pipelines right next to it. Conduits for energy and data. On and on and on... edding: In case you havn't noticed, linking myself, elsethreads: https://news.ycombinator.com/item?id=43131224 https://news.ycombinator.com/item?id=43131224