YAPI (Yet Another Plant Identification) request :-)

Ok, here's the rundown. I haven't actually seen this plant, just had
it described to me. Any of you know what it might be?

Floating plant. Leaves about fingernail sized, slight reddish
colouring, and often overlapping. Has flotation bladders about the
size of grains of rice. Quite thick root system. Apparently a Tropica
plant. Also apparently a type of ludwigia.

Ready, set, go!

 Len Trigg ===================================================
 Comp Sci Grad   DoD#1334  trigg at cs_waikato.ac.nz             
 Waikato Uni     GPX250    http://www.cs.waikato.ac.nz/~trigg/
 Finger trigg at jane_cs.waikato.ac.nz for PGP Public key