The first part of the documentary follows the development of a boy and girl, Jan and Suzanne, from birth to adulthood. At age 5, we see them getting into an open-air pool without swimsuits. They then play on the grass. Full rear and frontal nudity.
Two girls, approximately 9 and 10 y.o. invite a boy (11) to swim at the small private indoor pool. As they are giggling while stripping naked, the boy is doubting, whether he should do the same. Finally, he decides to join the girls, and all 3 of them have fun swimming.