An undine is a water elemental in several mythologies. In one such story, an undine's husband vowed to love her with every breath he took, but when he was unfaithful to her she cursed him to stop breathing in his sleep and die. Eventually, he passed out from sheer exhaustion and died.
This card seems to be the "basic form" of "Hydro Genex".
The name of this card was left untranslated in its Spanish prints.