:) if you have a super market that sells taro root, you can plant them in the baby bog, and have them make big, tropical looking foliage all summer- and then you can either dig up the tubers and save them for next year, or buy another $10 worth of them next year (theyr'e $1/lb where I am)

there's a few kinds of irises that like wet feet, as do marsh mallows (a hardy hibiscus)

but I'd go check the bog and pond garden forum, since that's what you have...

for bright color, sweet potatoe vines in pots give a lot of bang for their buck- and cascading from pots on the peir would be stunning looking :)