[neverdem]

A example is the Fort McHenry Tunnel, this is a sunken tube tunnel.

I'm not sure about how easy that would be with the Hudson. Ocean going ships go to the port of Albany.

[Rumplemeyer]

The tunnel is well below the bottom of the river, some of the East River subway tunnels are sunken tubes, built from the early 1900's thru the 1970's. As for ships, the Port of Baltimore is much busier than Albany and there are no problems.

As for constructability, the tunnels are buoyant, they “float” in the river mud, which is about 400 feet deep in the center of the Hudson at that point.