True, that river you see in my picture is only 100' from my garden beds. It keeps the soil warm and wet during the cooler months. The cable guys digging on my street are finding the (salty) ground water is only about 2' down. At high tide it is less.
I had far better success gardening when I lived in Columbia, SC, a climate much closer to yours. I teach Master Gardener classes and write a column for the local weekly and sometimes I have to fib about my enthusiasm for gardening in this part of he country. LOL