Idomeneo
Idomeneo is not lost at sea, but instead is saved by Neptune (god of the sea) and is washed up on a Cretan beach. There he remembers the promise he made to Neptune: he had promised to sacrifice (kill for the Gods) the first creature he should meet, whether it be a human or an animal.  The first person he meets is his own son, Idamante.  Because the two have not seen each other for a long time, they do not recognize one another at first. When Idomeneo finally realizes it is his own son he must kill, he tells Idamante to go away and never see him again.  Idamante does not understand why his father is saying this.  He is terribly upset, but runs off.  The Cretan soldiers get off Idomeneo's ship and are met by their wives, and all praise Neptune.