water-serpent, the Lernaean hydra, labour in vain
water-serpent, but esp. of the Lernaean hydra, Hes. Th. 313, S. Tr. 574, 836 (lyr.), 1094; Ὕδραν τέμνειν, prov. of labour in vain, because two heads sprang up for every one which was cut off, Pl. R. 426e: pl., but still with reference to the Lernaean hydra, E. Heracl. 950, Ph. [1136]: prov., ὕδρης ποικιλώτερος Herod. 3.89 (ἐπὶ τῶν δολερῶν Diogenian. 7.69).
II
name of a constellation, = ὕδρος III, Arat. 444, etc.