Trivia

Screenwriter Milos Macourek wrote the part of Matylda, the tyrannical head of the water-sprite family, specifically for Helena Ruzicková. However, the actress was politically undesirable at the time and was not allowed to film. For Míla Myslíková, who eventually played Matylda, it was a rare opportunity to play such a negative role.

The swimming pool that they built in the studios for the underwater scenes had a free space at the end with a water overflow and the architect built the decoration of the basement so that Jaromír Hanzlík went into the water and Milos Kopecký into the dry. The camera filmed everything at the level of the water, so that the difference between the dry and wet half of the staircase was lost with the right lighting.

Jan Libícek was originally cast as Jana's father Alois Vodicka. Unfortunatelly, the actor died suddenly on the set. His scenes were filmed again with Zdenek Rehor as Alois.

Miloslav Simek and Miluse Voborníková were briefly considered for the leading parts of Doctor Mrácek and Jana Vodicková, eventually played by Jaromír Hanzlík and Libuse Safránková.

Petr Markov offered the early version of his original story (which then was to be a semi-musical variation on 'The Little Mermaid', set in the countryside) first to Borivoj Zeman and then to Jaroslav Balík. Both refused.