Chinese marshflower is a very pretty, low growing, creeping perennial which is semi-evergreen to evergreen.  A native of the Himalayas it produces masses of white flowers on dense mats of deep green foliage from late spring right through the summer.  An excellent edging plant for the bog or very shallow margins and beach areas (not submerged), it is very useful for covering exposed pond liners.  Also available in its blue-purple form here

Height: 2-5cm

Spread: Creeping

Planting position: Very shallow pond margins (not under water) or bog garden in full sun or partial shade

Form: 9cm (0.5 litre) in a solid pot