After a cold night Water Chickweed (Myosoton aquaticum) is not at its best, it is a bit drooping. This little flower grows near water, as here on the Dordogne banks.
Often stinging nettles grow in the same spot, Water Chickweed is a bit more demanding, it needs not only a nitrogen-rich soil, but also a fair amount of water.
You could mistake it for another annual, Common Chickweed, that has the same kind of white flowers. Flowers, opposite leaves and pattern of growth look rather alike, maybe the Water Chickweed is a bit larger.
The day of this photograph the flowers were nearly closed because of the cold. The plant looks delicate but it can live and flower until deep into winter.