Aquatic plants that are not allowed to be grown/ propagated /sold inside South Africa:

Red water fern (Azolla filiculoides)
Dense water weed (Egeria densa)
Water hyacinth (Eichhornia crassipes)
Canadian water weed (Elodea canadensis)
Parrot's feather (Myriophyllum aquaticum)
Spiked water-milfoil (Myriophyllum spicatum)
Water lettuce (Pistia statiotes)
Kariba weed (Salvinia molesta)
Azolla microphylla
Azolla pinnata subsp. asiatica
Cabomba caroliniana
Hydrilla verticillata
Iris pseudacorus,
Ludwigia peruviana
Marsilea mutica
Nuphar lutea
Nymphoides peltata
Nymphaea Mexicana
Pontederia cordata
Sagittaria platyphylla

http://www.arc.agric.za/home.asp?pid=1031
http://www.apsa.co.za/board/index.php?topic=9271.0