Water-cress has become so popular as a salad addition that it is now cultivated on a wide scale. In the wild, it grows in shallow, fast-flowing streams and is an indicator of clean water.

Water-soldier grows submerged in ponds and open water, and pops up over summer, looking like the top of a pineapple! This rare plant displays white flowers and shelters many aquatic insects.

Look for the White water-lily in still and slow-moving water, such as ponds, ditches, lakes and canals. Its lily pads and massive, white flowers float at the water's surface.

Look for the Yellow water-lily in still and slow-moving water, such as ponds, ditches, lakes and canals. Its lily pads and cupped, yellow flowers float at the water's surface.

Found in ponds and marshes, the fragile look of the common water-measurer belies its fierce nature. A predator of small insects, it uses the vibrations of the water's surface to locate its…