Cursed Buttercup
Ranunculus sceleratus
Cursed Buttercup is so named because it is a highly poisonous plant. Even its species name, sceleratus, is Latin for polluted, profaned, defiled, and a lot of other nasty synonyms.
This native small-flowered buttercup is similar to the Littleleaf Buttercup (Ranunculus abortivus) but the basal leaves are a completely different shape and the habitat is much wetter soils.
Cursed Buttercup sometimes grows right out of the water
The basal leaves can float on the water
Naturally Speaking 