This was the original unaired pilot for the TV series Gilligan's Island. It is known as "Stranded", "Shipwrecked" and "Marooned" as it explains the start of the story, with the castaways getting shipwrecked.
Many differences occur in this pilot than the eventual series. The opening titles sequence is completely different and only lists the first four actors (Gilligan...and his Skipper too...the Millionaire...and Mrs. Millionaire...and the Other Tourists). The part of Mary-Ann, Ginger and the Professor are all played by other actors. Mary-Ann is called Ginger in this episode, Ginger is called Bunny and is a blonde, while the Professor is a ladies man-esque character.
The plotline of this episode was recycled and refilmed for the episode "Birds Gotta Fly, Fish Gotta Talk".
The first scene of this episode, with Gilligan discovering the crew trapped in the destroyed Minnow, was borrowed for the first aired episode "Two on a Raft". These means the original actors for Ginger, Bunny and the Professor can be seen (very) briefly in the aired first episode.
TBS eventually aired this special lost pilot on Friday, October 16, 1992 with a brief introduction by Bob Denver.
The Professor was a high school science teacher while Ginger and Bunny were both secretaries.