water dragon
/ˈwɔːtə ˌdraɡ(ə)n/noun
1Either of two aquatic plants with a spikelike inflorescence: (in early use) wild calla or bog arum, Calla palustris (family Araceae) (now rare ); (now, chiefly North American ) lizard's tail, Saururus cernuus (family Saururaceae).
2A mythical water monster.
3Any of several Australasian and Asian lizards occurring in the vicinity of water; especially the semiaquatic Physignathus lesueurii (family Agamidae) of eastern Australia.
Origin
Late 16th century; earliest use found in Henry Lyte (1529–1607), botanist and antiquary. From water + dragon.