Mayhaws, quince, maybe paw paws? Maybe jelly/pindo palms - as I see these things growing underwater in the swamps around here some times six months out of the year. I live in a swamp myself and actually have had success with growing apple trees as well, but there are a lot of warnings of root rot and such in wet areas. I've never had an apple tree die from having its feet wet, but you never know what could happen over time.

I also do muscadine grapes, persimmons, dunstan chestnuts, various types of mulberries, pineapple guava and experimenting with many types of blackberries and southern bunch grapes, but it's too soon to tell how they're going to do.

As far as citrus, I also have a bunch of citrus, but they're all in higher land. The one tree that I planted in one of the low spots died pretty quickly after a lot of rain. Also tried peaches, and they die when the first hard rain comes. I'm tempted to buy some half whiskey barrels to plant some peaches in.