After this hot and dry summer many lakes, ponds and reservoirs are dried out. The water has simply evaporated in the heat or - most of it - has been used by farmers to water their cornfields. It is normal there is less water in in summer than in spring, but this year really a lot of water disppeared. This is serious, and it created real problems for many natural habitats and the species that are dependent on them. But there are exceptions, like this Water Germander (Teucrium scordium). It is abundant this year.
It grows in wet habitats where the water level changes during the year, as here in a large reservoir. You won't find it in the center of the lake; there is always water, even in the hottest of summer. You won't find it either near or on the edges because there it is too dry. But between the two, where the water retires more and more during summer, it thrives. Its underground roots stay alive during inundated periods and when the lake dries out it makes new sprouts and also a lot of stolons in the drying mud with which it spreads over a large surface.
Like al germanders, it has flowers with only one lip, the lower one. The leaves have rounded dents and they are very downy. Like many flowers of the Lamiaceae family, Water Germander is aromatic.