This link on rain gardens may help. There is a link for each region in NC that shows trees, shrubs and perennials with tolerance for water on a 1-3 scale.

Here is a link that might be useful: rain gardens

Bald cypress, pond cypress, red maple, loblolly pine, sweetgum, water tupelo, holly, sycamore, hawthorns.

My favorite tree for that type area is the sweet bay magnolia (magnolia virginiana). Mine is budding up right now and I can't wait for the sweet fragrance. I'm in Chapel Hill and it stayed evergreen here.

What you might want to use under whatever tree you plant are some florida anise bushes. They stay evergreen,are completely ignored by deer and rabbits(and bugs) and have a neat flower too. They tolerate my rain garden area(underwater sometimes).

Other shrubs to use are Clethra and Itea, as well as some of the Leucothoes. Pussy willows would like it too.

Thanks all for your suggestions. I will pass them on to my friend. I hadn't thought about a rain garden, thanks for the link. Linda

I have illicium (anise) in my rain garden and the deer munched it all winter. It is on the deer-resistant list and they had never bothered the other 3 next to my house, so I thought it would be safe out in my rain garden. It isn't dead, but all the leaves were eaten. It should come back.

I also have 9 itea 'Little Henry' in my rain garden and they are great little shrubs. This is the first spring (planted last fall when they were brilliant red) and I'm looking forward to the blooms.

Also try Willow Trees, Ironwood, River Birch.

Linda, is it wet all the time?
Many trees can tolerate an occasional flooding but won't last long if planted in permanently soggy soil. There are lots of lists of plants/trees for that site on google.
Many hollies , especially dahoon and yaupon, can survive well in soggy locations as long as they get good sun. That's another factor to consider as well as what kind of trees are already there on-site.

If your friend has sandy soil a fever tree (Pinckneya bracteata) would be neat if you can get a hold of one. The NC Botanical Garden often has them for sale and I imagine places like Greer or Woodlanders might have them too. They like wet sandy soil and have pink flowers in summer like poinsettias. For trees they have rather short-lived (about 20 years) but easy as pie to grow from seed.