Granddad Acrisius had read a horoscope warning he would be killed by the child of DANAE. So he shut them both in a box and chucked them in the sea.
Wooden boxes float and fishermen catch all manner of odd things in nets — they ended up on a tiny island just big enough to have a king, Olydectus, and all went well.
PERSEUS grew up and, being a get-ahead kind of fellow, set off in a boat to have adventures. Naturally to do this he’d put in a grant for Heavenly Aid. The Stygian NYMPHS provided suitable equipment: a helmet of invisibility from HADES, a shiny diamond sword from HERMES, and... a scruffy old bag from the tool shed.
From this exploit he gained PEGASUS the Winged Wonder Horse, born from the blood of MEDUSA. (Somewhere along the way he got into an argument with ATLAS and used MEDUSA’s head to turn him to stone. For which ATLAS was very grateful.)
Finding he was very good at this sort of thing, and having great confidence in his equipment, he went in for the full thrilling hero career rescuing ANDROMEDA from a frightful Sea Dragon (so many years before that copycat St George).
He became extremely popular, never refusing to sign autographs or speak to reporters, and was always hoping this would ensure the possibility of being taken on an Olympus Trip. His grandson EURYSTHEUS became King of Mycenae and was an utter coward to the embarrassment of all concerned.