Swallows and Amazons (1974)

In 1929, four children on holiday with their mother in the Lake District are given permission to sail their dinghy, Swallow, to a nearby island and camp there for a few days. Their adventure soon turns into a spirited rivalry when they discover that two other girls, who sail the Amazon, already consider the island their territory. As the two crews face off, their games of sailing and mock sea battles take on a life of their own.