Years ago I managed to grow a respectable clump of baby's breath (Gypsophila paniculata) in my first garden, which was both sunny and cottage-y. These days I grow a water-loving version of the plant. Actually, it's a completely different family but offers an airy flower stalk that visually refers to the traditional garden version.
Alisma triviale grows in a few inches of water right at the stony edge of our pond. I put in one plant in 1998 and each summer they festoon the pebble beach. They are not so prolific as to be a problem. And they are easy to pull out if I decide one is blocking the view to the water. These will start blooming soon, with flower clusters at the ends of all the branches of this tree-like water plant.