We have a large section of the garden here that is more or less permanently boggy, and we've established lots of plants that love it and tried a few that have died.

There are quite a variety of plants, big and small, that thrive in these situations, just like they do in the wild, depending on how big your area is and how much sun/light it receives.

Shrub wise Cornus alba, Salix alba, Viburnum opulus and Aronia melanocarpa are all ideal candidates.

Carex pendula likes boggy ground, and willows drink a lot, should you have room.

Did you see Monty Don had a very boggy area in his garden ? I noticed he had helebores growing there, and dont hydrangers love water.

also iris and geums I think.