A fast growing annual weed also known as Celery-leaved Buttercup. It is native to Europe and North America. In the US the semi-aquatic or aquatic form (forma natans) can be found along the Missouri, Mississippi and a few other rivers of the USA.
This virulent weed prefers moist micro-habitats. The whole plant is acrid, anodyne, antispasmodic, diaphoretic and emmenagogue and rubefacient. When bruised to the skin it may raise blisters and creates sores on the skin of allergic people, which are by no means easy to heal. If chewed it inflames the tongue and produces violent effects.
Consequently in the USA for example Rhode Island and Connecticut State classify it as a species of special concern.