Flowering time:
July - August.
Aquatic perennial. Native.
White flowers with purple spot at base of petals.
Long-stalked, arrow-shaped aerial leaves.
Floating oval-lanceolate leaves, linear submerged leaves.
Height: 30-90cm.
Found in still or slow moving fresh water.
Occasional to locally frequent in most parts of Ireland.
Correction:
Photographs are probably Canadian Pondweed, S. japonica