Called Garmin Techsupport again, and rehashed my issue about the Guide to option not working in the Savannah, Ga area . This is because at mean low tide some areas between where I am and where I want to go is less than 6 feet at mean low tide. That issue is being addressed and enhanced. The tech rep told me they built 6 feet into the software for safety.
But when you set up "your boat" you tell the unit your safe depth, which for me is 3 feet. I am assuming that is the change they are going to make, to use your safe depth instead of a constant 6 foot.
The Tech rep gave me his name and said when the new chip is available - probably 6 mos, to call him and he will do a warrenty swap at no charge. So Garmin recognizes a problem and is willing to do something about it.