Did you ever consider that they may use VHF/UHF frequencies not tied to marine? Or, have you just programmed in the VHF marine frequencies and do the search and find out for yourself? Isn't that the essence of scanning? Finding who uses what frequency. It's always been the fun part for me. Larry
If you want to listen to the ships going up/down river from the ports and being moved around in the port area, the best places to start will be Ch. 13 (156.650) and Ch. 14 (156.700). You'll of course want to have Ch. 16 (156.800) programmed in as well. You'll definitely want to search through the other Marine VHF frequencies because you never know what might pop up.
You will hear more USCG Auxiliary activity on Ch. 21 because most (but not all) of the USCG activity has moved to the Rescue 21 system in the Savannah area. Much of the Rescue 21 activity in the Savannah area is encrypted, but there is still some unencrypted activity (particularly the small boats). The Rescue 21 frequencies in use in Savannah are CG 113 (163.1375) for Station Tybee, CG 410 (413.000) for Air Ops, and CG 107 (150.300) for Coast Guard Air Station Savannah. Remember that those will be digital.