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The Blue Lagoon (1980)
Plot
Two young children are the sole survivors of a shipwreck in a time when sailing was the only way of travel. They are stranded on a tropical island, a real paradise. Together, Richard and Emmeline have to survive, which is quite easy as there are no dangerous animals on the island. Years later, the two teenagers are living in a self-constructed hut, strange emotions start influencing their relationship..
Although they had no grown-ups to educate them for all that time, the behaviour of the two always stayed in a very civilized way. Nature takes its course, and Emmeline gets pregnant, totally unaware of the fact that a child is growing inside her. On the night their boy is born, Richard finds out about the origins of the drums they hear from time to time from the forbidden side of the island.
Imdb (5.1/10) Imdb link