Q:

How does GIS intervene in ports and coastal areas?

I guess my question is pretty clear and yet broad, but what I was kind of hoping for is some insight on how GIS would be helpful in managing the ports or coastal areas. I can imagine it could serve monitoring the environnement surrounding the port, it could for example use satellite imagery for exploring the bathymetry of the coasts, etc. 
So, how does GIS and marine geographical information rhyme ?
P.S : would be great if every poster used her/his answer for one application. 

A:

The US Navy used GIS in a study Assessing the Impact of Future Sea Level Rise on its facilities.

