Thanks for the links, but unfortunately they aren't the aquatic versions of marigold and buttercup that I am looking for. I would consider both of these as wetland, or semi-aquatic plants. The two that I would like are Ranunculus longirostris (
common names include water buttercup and white water crowfoot) and Bidens beckii
(commonly called water marigold). They look and grow similar to Myriophyllum
species, and I've often been sent samples of them by people worried that they're Eurasian Watermilfoil.
I've attached a few photos of each, they both produce a nice tiny flower in mid to late summer, and the buttercup can smell quite nice.
The neat thing about B. beckii
is that the flower spike will also create emergent, free-standing leaves...something not often seen in aquatic plants, at least around here!
The top two pics are R. longirostris
and the bottom two are B. beckii
. I'm guessing they aren't commonly cultivated, but I'm always keeping my eyes peeled as I'd love to try and get them to flower!
To answer your question Angel, the links posted probably wouldn't survive long fully submerged, but these two would since they're true aquatics.