The symbol of Warsaw (Warszawa, in Polish) is the mermaid. This statue is in the middle of the Old Town Market place.
A pair of mermaids in 1980's Warsaw are actually main characters in the 2016-2017 Polish-language film The Lure (in Polish called Córki dancingu), which is apparently the first musical in Polish cinema.
There are however other mermaids around the city. The mermaid at the Vistula river (below) was designed before World War II (see link) by Ludwika Nitschowa. The model for that mermaid statue was Krystyna Krahelska (born March 24, 1914), a young poet who during the war became a nurse and currier for the Polish Underground Home Army (Armia Krajowa).
On August 1, 1944, the day that the Uprising began, she was trying to help an injured collegue when she was shot in the chest three times. She was taken to the insurgent hosital but died of her wounds on August 2nd, the second day of the 63-day-long Uprising, at the age of 30.