Zantedeschia elliotianayellow calla lily. Information of Plantzafrica website leads me to believe that this is species Z. elliotiana, although I have been know to be wrong about these things. Photographed in a private garden in Berkeley, CA
Betimes known as the Upright Elephant's Ear, this species is reported from parts of Central America and from the western Amazon Basin. Photo from Eastern Ecuador.
Family: AponogetonaceaeDistribution:Tropical Asia and AustraliaCommon in ponds and ditches.Submerged aquatic herbs. tubers globose, Leaves 3-11x 1-2.5cm, linear oblong, base cordate, petioles 10-20cm long. Flowers 3-4mm across, pink/violet 4-5mm across, on dense spikes, peduncles 10-30cm long, Boiled tubers are eaten.Reference: Flora of presidency of Madras by J.S Gamble, ENVIS, Flora of Nellore district By B.Suryanarayana &A.S Rao