If you are looking for evergreen shrubs than Sarcococoa humilus would be the fragrant answer but for winter color the yellow twig or red twig dogwood would stand out with brilliant bark. Astilbe are perennials that love moist soil and some iris and the huge leaved gunnera plant would also adapt to a wet area. You may want to add a few inches to a few feet of soil to keep the new plants above the water table so their roots don't rot - if that is not possible consider a bog garden using skunk cabbage, rush, willow and other wetland plant material. Keep growing, Marianne Binetti