The choppy water problem while running the AICW’s passage across Georgia’s St. Andrew Sound results from the Waterway’s passage practically out into the briny blue, in order to clear Horseshoe Shoal, which occupies the Sound’s mid-width. Recognizing the potential for very dusty crossing here, the US Army Corps of Engineers has provided an alternate route, known as Umbrella Cut, BUT low water depths on this passage can run as thin as 4 1/2 feet.
The exchange of views below has been copied from the T&T (Trawlers and Trawlering) list.

My progress south will take me across St. Andrews sound on Wednesday. Marine weather forecast for the area is NE 10-15 knots seas 4-6 off shore, choppy inland. What would you expect the sound to be like?
Bob
Chateau de Mer

Any east wind will cause issues particularly if in opposition to the tide e.g. ebb. There is an alternate route that is doable depending on stage of tide and draft of your boat. 6′ in St Andrews is very short and mean. Enjoy the Golden Isles and cut the shoal at your own risk if crossing the sound.
Joe
M/V “Carolyn Ann” GH N-37

We went through the area yesterday. It was beyond awful in the Sound, so we turned to starboard up the Satilla River to marker 8, turned to port and worked our way through the deeper water back to Cumberland River. This is NOT the charted alternate route, but much shorter and worked for us. It was about 2 hours after high tide and we were able to make it through. We draw 5′. Not flat, but the giant elephants in St. Andrews made it a no-brainer for us.
Take a look, and good luck!
Stephanie Wakelin
M/V September Song

We traveled through this route [Umbrella Cut] today about one hour after a 7′ high tide. We draw 6′ and never saw less than 5.5′ under our keel. Nice alternate to the breakers rolling in the sound.
glebreton

Click Here To Open A Chart View Window, Zoomed To the Location of the AICW’s Passage Across St. Andrew Sound