Cannas would be the perfect choice...... they can even be grown in water sometimes, like water lillies. They love water, heat and sunshine. I live in Cache Valley near Logan. I grow hundreds of them. Enough to sell some at a couple of nurseries. I have to dig mine up every Fall in my climate, but in zone 7 they may survive in the ground if you mulch them well. I've got plenty to give you if you ever make it up to Cache Valley. I also grow taro (elephant ears) bananas, palms, bamboo, etc.

You might also consider Colocasia esculenta and it's hybrids/cultivars if this area is mostly moist to dry in the winter. If soggy wet in the winter time the tubers from which the plant grows will rot. They are commonly called Elephant Ears and the specie mentioned is commonly sold now at the box stores. Their cheap so a few won't cost much to try. Go to Google click images and enter the full name if not familiar with this plant. Their hardy to zone 6 and many here in the NE grow them successfully. If you try them it's to early to plant them outside since they wouldn't have acclimated to the cold coming from inside a warm store. They should be potted up and given a small amount of water and kept in a bright sunny area that is warm until they start growing. When all danger of frost has past they can be planted in the ground. If the soil is not always moist or wet you will need to water if you want them to grow to their full potential. If your looking for a tropical plant that requires no care there is no such thing other than cacti which would perish in a wet area. Let me know if you have any questions.

Scott

Fatsia japonica, if you can mulch it for the winter and it is an area with some cover - Tetrapanax papifera if it's full sun and no cover is available. Calla lilies would probably do well during the summer but you might need to pull rhizomes in the winter. Irises could be fine - they may not be as tropical as you'd like but could be a decent accent point. Berginia cordyfolia has nice tropicalesque foliage and beautiful flowers, and likes wet soil and shade.
Lots out there - check:
http://catherine-kaufell.suite101.com/growing-showy-perennials-in-a-wet-garden-area-a222633
http://www.cooltropicalplants.com/
http://zonedenial.com/
Good luck!

Thanks everyone! very helpful information. The area is bone dry in the winter and always wet in the summer so some of these might do swimmingly. We have flood irrigation from May through October that keeps the area very swampy, but as soon at the irrigation stops flowing the area dries out completely. I don't mind giving plants extra care and in fact already have woodchips down there so I could just pile them high in the winter to protect more tender plants.