Hylas was a young companion of Heracles, no more than a boy. Depending on the version, Hylas was either an eromenos (lover) of Herarcles or an illegitimate son of the demigod. He joined Heracles among the Argonauts, becoming the youngest member of the crew.
Hylas was extremely beautiful. On a certain stop of the Argo, he went searching for water. Nearby water nymphs fell in love with him and abducted him. Hercules searched for him in vain for a long time, quitting the Argonauts to maintain his search. Gaius Valerius Flaccus believed that the nymphs shared both their love and immortalitry with Hylas.