So many factors and (fun) challenges!
What's your sun/shade for the spot? And how large an area. Both asked above.
Work with your givens, that being pond, fence, and shrub (camellia not native but lovely). Looks to be limited in space and sun, also the camellia (or any shrub) will be sucking up water and nutrients. Hard to get into and work, so want easy, take care of themselves type plants.
Flowering for more than a few weeks at a time is hard there. Most perennials flower perhaps 6 weeks. Think of foliage plus some flowers. Yarrow and/or Queen Anne;s Lace both sunnier and drier, think meadow. Coneflower has a fairly long bloom time, and my experience can take some shade, not picky about watering, spreads some. aka easy. Another I like for a whatever space is anise hyssop. Self seeds some, not obnoxious, and blooms much of the summer to the favor of pollinators.
If this is afternoon shade check out Solomons Seal and also some native ferns. Both would be pretty with the water feature.