[OhioGuy]

^^ A floating underwater tunnel? So something that doesn't rest on the ground, but instead is somewhere in the middle between the surface and ocean floor? Doesn't sound very safe to me. Even if it's low enough to avoid large ships, whales also enter San Francisco Bay from time to time. What happens if one of them hits the floating tunnel? I wouldn't want to be on a train going through that tunnel at that time.